How do parties really choose candidates in the US?

Question

When I was growing up, I was under the impression that America’s candidates for President or Congress are chosen by primary elections. After watching the news more carefully, I later got the impression that presidential candidates are chosen by delegates at party conventions. However, I have picked up on a few things over the years that make it seem as if primaries or conventions are not the ultimate authority on who becomes a candidate. For example:

1. When Donald Trump was running for re-election, some states canceled their Republican primaries and chose Trump outright as their nominee.

2. When Trump ran against Hillary Clinton, some never Trumpers advocated that the Republicans disregard the primary and choose someone else.

3. I know that party candidates have been selected by different mechanisms throughout history, and I am under the impression that changes in these approaches were internal party decisions (rather than via binding laws).

4. I have read in various places that parties have the ultimate say in choosing their nominees, and they are not required to select them by primaries/conventions if they decide not to.

It seems that beneath the pageantry of America's primaries and conventions, certain party insiders are the ultimate authority on who becomes their candidates for President and Congress. These insiders may have adopted rules that primaries/delegates determine their nominees, and there are surely political reasons why they want to keep things this way; however, if these insiders are technically allowed to change those rules, then in my mind the insiders are the ultimate authority on selecting candidates. Regarding this, I have the following questions:

1. Who are these insiders? Are they elected representatives, national party chairs, or maybe someone else?

2. Can these party insiders exercise the same sort of control over their parties as many parliamentary governments can? (e.g., total insider selection of candidates, the ability to kick elected representatives out of their party.) I know there are political reasons why they wouldn't do this, and maybe there are internal party rules forbidding this; however, if these insiders are technically allowed to change party rules to allow for parliamentary-government-level party control, then in my opinion the answer to this question is "yes."

3. How does this all work for state-level governments?

EDIT: I rephrased my questions to clear up some of the confusion about them.

Answer 1

U.S. elections are complex, especially presidential ones, which have several layers of indirection. Because of the complexity of the question, I'm going to focus on the case of presidential elections. (There are important differences between presidential elections and all other kinds of elections.)

I also want to note that although insider selection of candidates was formerly common, the fact that it is possible in theory does not mean that parties could easily transition back to this method of selection. Also, attempts to disregard the results of state primary elections and thereby reduce the level of democracy (as indirect as it is) in the process could conceivably be subject to judicial review or regulation by state or federal legislation, although this would probably raise constitutional questions about the scope of power of different government branches over the nomination process.

It seems that in formal terms, the key moment when party "insiders" would be able to exert influence is when the rules for the national convention of party delegates are adopted. In the case of the 2016 Republican National Convention, the rules committee included delegates from each state, territory, and Washington, D.C.; but I assume the makeup of equivalent bodies and the method for selecting the delegates could vary depending on the party or perhaps from state to state.

Hopefully someone else can provide further details.

Links to some related prior questions:

• Is the Republican Party forced to support whoever wins the presidential primary?

• Are there any rules or laws requiring the a party to hold primaries if they have an incumbent running for reelection?

• Does the GOP candidate with the most delegates have to be the nominee?

• Is Donald Trump officially the Republican nominee [as of May 7th]?

My current attempt to answer the numbered questions is as follows:

1. Who are these insiders? Are they elected representatives, national party chairs, or maybe someone else?

• It seems like it would be whoever sets the rules for the national party conventions; but I don't know details of who these delegates are or can be in general. So I can't say who specifically in the parties would have the power to change who is nominated.

2. Can these party insiders exercise the same sort of control over their parties as many parliamentary governments can? (e.g., total insider selection of candidates, the ability to kick elected representatives out of their party.) [...]

• No; the role of political parties in the presidential nomination process in the United States is not comparable to party control in parliamentary governments. The parties play a role in the election of the president, but I believe parties have no legal influence over an elected president, only political influence. Within a legislative body, such as the houses of the United States Congress, parties have a "caucus" that can play a more similar role to parliamentary party discipline.

3. How does this all work for state-level governments?

• Nominees to state-level positions are not selected by national party conventions. I'm not sure what the main opportunities for party insiders to influence such elections would be: in some cases, it seems parties are responsible for submitting the names of candidates for primary elections.

Presidential elections

General election ballot access for presidential elections

The President of the United States is elected by the electoral college, and the Constitution gives state legislatures the power to direct how a state's electors are appointed. So after the electors are appointed, I am not aware of any way that parties could play an official role in US presidential elections. Affiliation with a party is not technically a prerequisite to become president, so even if there were a way for a party to officially expel a member (I'm honestly not sure if there is), it wouldn't have any effect in and of itself on that person's ability to be elected president (although, like anything else, it might conceivably influence the decision of the Electoral College).

Per Wikipedia, "In practice, the state legislatures have generally chosen to select electors through an indirect popular vote, since the 1820s."

Therefore, the ultimate point of a party nominating a presidential candidate is to get the states to appoint electors that will vote for that candidate, which requires getting the candidate on the ballot in each of the state-level general elections.

The rules for who appears on a ballot in elections are called "ballot access". Ballot access laws are made by states, subject to judicial review by the Supreme Court. This includes rules for which candidate appears on the ballot as the nominee for each political party. (There are also rules for independent and write-in candidates, which are not relevant to your question.)

The National Association of Secretaries of State has the following summary for how general election ballot access works: SUMMARY: STATE LAWS REGARDING PRESIDENTIAL BALLOT ACCESS FOR THE GENERAL ELECTION From skimming, it appears to me that most states have chosen to give a large role to political parties here.

As I said, I'm focusing in this answer only on presidential elections, but it seems worth noting here that states are under no obligation to carry out general elections that follow the format of having at most one candidate nominated per party: for example, as Anonymous Penguin pointed out, California has a "jungle primary" system for most positions, including U.S. Senator, where the top two candidates in each primary, regardless of party, advance to the general election.

Here is a PDF laying out the general election ballot access rules for the state of Alabama that applied in 2012. The requirements for political party nominations were as follows:

1. Political Party

Any political party’s national convention or other like party assembly having state ballot access for the general election may nominate. To qualify for statewide ballot access, a political party must:

• Receive more than twenty percent (20%) of the vote cast in the state at the last general election. (By this method, only the Alabama Democratic and Alabama Republican parties qualify for statewide ballot access in the 2012 election.) [§17-13-40]

• File a petition by March 13, 2012*, with the secretary of state containing at least 44,828 signatures of qualified electors. The number of petition signatures for statewide ballot access must equal or exceed three percent (3%) of the electors who cast ballots for the office of governor in the last general election. [§17-6-22(a)(1)]
  Parties submitting a petition must also:

  • File with the secretary of state an original copy and a copy in digital format or other electronic format acceptable by the Secretary of State of the party’s emblem by September 7, 2012. [§17-6-29]
  • Hold a mass meeting, beat meeting, or other like assembly to nominate candidates for public office or delegates for a convention at which candidates would be nominated. A public notice of the time and place must be filed at least five days prior to the meeting date with the probate judge in the county where the meeting will be held and published in a newspaper of general circulation in the county at the expense of the political party. [§17-13-50(a)-(b)]

The certificate of nomination issued by a political party convention must be signed by the presiding officer and secretary of the convention and by the chairman of the state executive or central committee of the political party making the nomination.[§17-14-31(b)]

So for Alabama in 2012, it seems like the signatures of specific officials from the convention and from the state executive or central committee of the political party are required.

For comparison, here is a form I found titled "CERTIFICATE OF NOMINATION PRESIDENTIAL ELECTORS To be used by political party established in North Dakota":

I, [chair of state convention or state party chair] do certify that I am the [] chair of the state convention [] state party chair of the [party name] Political Party of the State of North Dakota and that on [date of nomination], 20__, the following individuals were duly nominated as Presidential Electors by the [party name] Political Party, duly convened in accordance with the bylaws of [party name] Political Party and the laws of this state

It's completely unclear to me whether "duly convened in accordance with the bylaws of [party name] Political Party and the laws of this state" is enforceable in any meaningful sense. I'm also not sure if the linked form is the one used by the Republican and Democratic parties, or if it might only be for use by smaller parties.

I'm not going to try to find comparable information for all other 48 states.

The Democratic and Republican national conventions seem to be the "last stop" before the presidential selection process moves out of the hands of the parties

The nomination process followed at the national conventions is set by party rules, not state laws, but both parties' rules assign an important role to pledged delegates who are expected or in some cases legally bound to vote for the candidate who won the primary election or was selected by caucus in their state.

There seems to be quite a bit of detail at Wikipedia on the Democratic National Convention and Republican National Convention.

Parties clearly have quite a bit of freedom to determine the rules for their nomination process, but there seems to be some uncertainty about whether this process is completely exempt from regulation by the U.S. Congress or by state legislatures.

Opponents of congressional action generally point to two Court cases that support the primacy of political parties in setting their own nomination rules. In Ray v. Blair (1952) the Supreme Court ruled that it was constitutional for a state to allow a state party to make potential electors to the electoral college sign a pledge of loyalty to that party. In Cousins v. Wigoda (1974), the Court ruled that political parties have the authority to set their own rules for their nomination process, including the rules that determine how delegates are seated at the national convention, and that such party rules trump state laws.

("Why is the presidential nominating system such a mess?", Elaine C. Kamarck, pp. 5-6)

There's some information about the efforts to avoid nominating Trump in the Wikipedia article 2016 Republican National Convention:

The Rules Committee, which sets the rules of the convention and the standing rules that govern the party until the next convention, met on July 14. The rules it passes must be adopted by the full convention to take effect. This committee is regarded as the most powerful. It consists of 112 members, including one male delegate and one female delegate from each state, territory and Washington, D.C. Members of this committee are elected at state conventions. The Rules Committee was chaired by Enid Mickelsen of Utah and Ron Kaufman of Massachusetts.

In June 2016, activists Eric O'Keefe and Dane Waters formed a group called Delegates Unbound, which CNN described as "an effort to convince delegates that they have the authority and the ability to vote for whomever they want." Republican delegate Kendal Unruh led an effort among other Republican delegates to change the convention rules "to include a 'conscience clause' that would allow delegates bound to Trump to vote against him, even on the first ballot at the July convention." Following a "marathon 15-hour meeting" on July 14, 2016, the Rules Committee voted down, by a vote of 84–21, a move to send a "minority report" to the floor allowing the unbinding of delegates, thereby guaranteeing Trump's nomination. The committee then made the opposite move, voting 87–12 to include rules language specifically stating that delegates were required to vote based on their states' primary and caucus results.

From what I can see, it seems to have been a desperate measure that had little or no realistic chance of success. However, I don't have a detailed technical analysis of this scheme. I think it's likely that any astonishing maneuvers would be challenged in court, but I don't know whether such a challenge would succeed. The Wikipedia article on Delegates Unbound says

According to the group, "There is no language supporting binding in the temporary rules of the convention, which are the only rules that matter" and "barring any rules changes at the convention, delegates can vote their conscience on the first ballot." The group's co-founder, Eric O'Keefe, said, "Our goal is simple, to ensure the delegates are not misled to believe they must follow orders or rules set by others." O'Keefe added that he believes state laws and state party rules purporting to bind delegates to a particular candidate based on primary or caucus results are unenforceable and would lose a court challenge.

Another useful summary is laid out here: The U.S. Presidential Nominating Process (Council on Foreign Relations)

Primary elections are an optional preceding step before the nomination of a candidate for a general election; whether to have a primary is up to the party, but parties do not have total freedom to dictate how a primary is carried out

Currently, many states have primary elections, which create some blurring between what can be viewed as public and private actors.

Primary elections are carried out at the state level and under state law. Parties may choose not to participate in a primary election in a particular state; this choice applies at the state level and the details of how it works may therefore vary by state. (It might be as simple as the party just not submitting any candidate names to the state: e.g. it seems that Florida leaves that entirely up to the parties.) A specific example of a state where the Republican Party canceled its primary for the 2020 presidential election is South Carolina. Here's a news article that mentions some other states.

However, when a primary is held, parties do not have unlimited rights to restrict who participates in "their" state primary election: in Smith v. Allwright (1944) the U.S. Supreme Court held that it is not allowed for a party to use racial criteria to exclude voters from a state primary election. On the other hand, the Supreme Court has struck down state laws that required parties to allow non-party members to participate in selecting the party's nominee (California Democratic Party v. Jones, discussed further by Magarian below). Another recent case that seems relevant is the lawsuit by the Republican Party over Utah's Elections Amendments Act of 2014 ("SB54"), which affected the primary process; it reached the United States Court of Appeals for the Tenth Circuit which affirmed the act, and the U.S. Supreme Court declined to hear the appeal.

Kamarck (cited above) discusses some of the development of the current process of selecting presidential candidates, how it is subject to judicial oversight, and how it may be regulated by states or potentially even by Congress:

For much of American history, political parties and their activities were treated as private, not public, matters. Indeed, prior to the widespread use of binding presidential primaries—which didn’t happen until the 1970s—the entire pre- reform-era nomination system was essentially a semi-private, if not entirely private, enterprise. As state legislatures introduced primaries at the turn of the century, spurred on by the Progressive reform movement, the result was a certain degree of regulation through statutes creating the primaries. But by and large the federal government stayed out of the business of party nominations at all levels.

Then, in 1944, the Supreme Court ruled in Smith v. Allwright that political parties are state actors and cannot discriminate. At the time, many southern Democratic state parties restricted participation to whites, effectively disenfranchising African Americans. By prohibiting them from voting in primary elections, the state parties, for all practical purposes, prevented African Americans from having any say in the electoral process, given the Democrats’ uncontested control of the South. The Supreme Court saw a compelling interest in protecting the right to vote and intervened to prohibit all-white primaries. The Court has also intervened in the political process in several other important cases. In Burroughs v.United States, decided in 1934, the Court found the Federal Corrupt Practices Act constitutional on the grounds that Congress had the authority to protect the election process from corruption. Similarly in Buckley v. Valeo (1974) the Court ruled that parts of the new campaign finance law were constitutional because they empowered Congress to prevent corruption in the nominating system. And in Oregon v. Mitchell (1970) the Court ruled that states had the power to extend the right to vote to those who were 18 years old.

(pages 5-6)

Some Supreme Court cases regarding rights of association for the parties in primaries are discussed in this article: "Regulating Political Parties under a "Public Rights" First Amendment", Gregory P. Magarian (April 2003; William & Mary Law Review Volume 44 (2002-2003) Issue 5, Article 2).

Answer 2

Essentially how political parties nominate their candidates is up the parties and not regulated by law. Both Democrats and Republicans often choose to hold primaries because it may help them to find candidates that are popular. But whether they do that, who is or isn't allowed to vote in the primaries and who is or isn't allowed to be on the ballot list is entirely up to the parties.

Answer 3

Technically, the parties choose their candidates at the conventions. When voters vote in primaries, they are actually selecting delegates to the national convention who have pledged to vote for one candidate or another. This is analogous to the Electoral College system for the general election. Voters are technically choosing electors pledged to one candidate or another.

But, while the votes cast by the Electoral College have been a pure formality since the early days of the US, the controlling effect of the primaries has only been a phenomenon of the past fifty years. Before 1976, and certainly before 1972, there was real doubt about the nominee until the convention happened. There was a time when not every state had a primary, and candidates didn't always formally compete in each primary. Also, delegates were only pledged to their candidate on the first ballot. If no candidate reached a majority, additional votes would be taken until a majority was achieved, and delegates were free to vote for whomever they chose.

An additional complication was that not all delegates were chosen in primaries. To some extent that is still true, but I am not qualified to explain the details.

One thing to keep in mind is that the parties evolved as self-selected groups of people who would propose slates and try to get voters to choose the entire slate (representatives, state officials, and president). Sometimes even today you will see organizations outside of polling places passing out lists of candidates they want you to pick in a primary election. In the beginning, there were no primaries at all, and parties operated sort of like that. Over time, as the parties became a part of the system, primaries evolved and voters began to expect full say over the nominee. In 1976, Carter ran in every primary and it became clear that any attempt to turn the tide at the convention was no longer possible.

This answer gives more history than it does explicit rules about what has to happen, but I think an understanding of the history helps you understand the internal logic.

Answer 4

As I read the question, it’s taken for granted that the American system is a duopoly between the Republican and Democratic parties and ballot access is not what the questioner is concerned about. The short answer is that candidates for Congress are chosen by state voters the same as candidates for other offices in that state, and the choice of Presidential nominees is different. No Congressional or Senate district crosses state lines so each is under the jurisdiction of a single state. Thus answer to how candidates are chosen for Congress is also the answer to the bonus question. I will start with the bonus question.

Because there are 50 states, there may be more than 50 different ways that it works at the state level. To give one example, in Wisconsin there are non-partisan elections for municipal and judicial offices and partisan elections for non-judicial county and state offices and for the federal legislature. Non-partisan means no party label appears on the ballet next to the candidate’s name. The elections to the state supreme court are legally non-partisan even though it’s widely publicized which side the candidates support. The non-partisan elections have primaries in February and general elections in April, while the partisan offices have primary elections in August and general elections in November. The November election is required for federal offices by the federal constitution and laws, while the other dates are up to the states. I’m not aware of a state that does not normally hold general elections for state-wide offices in November, although that must be up to each state.

For Wisconsin non-partisan elections, if more than two candidates file and are approved to be on the ballot, a primary will be held in February with all candidates on the same ballot and the top two candidates moving on to the April ballot. The partisan elections are different. In the August election you have races for each office and for each party. Often there is only one candidate in each race, for example you might have one candidate for governor on the Democratic ballot, two on the Republican ballot, and one on the Libertarian ballot. The candidate who wins a plurality in each race becomes that party’s candidate for that office in the November election. The November election is also won by a plurality of the vote.

There are differences between states in how you choose which party’s primary you wish to vote in. In Wisconsin voters do not declare a party when they register, although in some (maybe most) states you do. In Wisconsin, you receive a ballot with all parties’ races on it but your votes in primary races are only counted for the party you choose at the top of the ballot. In other states that do not register by party, you may have to declare your party selection to workers at the polling place and receive a ballot with only the races for that party. But that choice is only binding on you for that election and you can choose a different party at the next primary election. New York is a state where voters are registered by party. Ivanka Trump was not allowed to vote for her father in the New York primary in 2016 because she did not change her registration in time.

To give some extreme examples of different primary procedures, California uses a so-called jungle primary system where all parties appear on the same ballot and the top two advance to the general election. This often results in two Democrats facing each other on the general election ballot and no Republican. Alaska also uses a jungle primary system with the top four candidates advancing and the general election using a ranked choice or instant runoff procedure to determine the result. Louisiana also has a form of jungle primary, but the primary is on the same day the rest of the country holds the general election, and a candidate who wins an outright majority in the primary is declared the winner. Iif no candidate wins a majority, the top two advance to a runoff in December. From the late 1970s until the 1990s, the primary was held in September or early October with the runoff in November, but the federal Supreme Court ruled this violated federal law because a winner could be declared before the legal November election date based on only the primary election.

In a jungle primary, arguably the party label is meaningless and is included only for identification purposes.

Georgia and some other southern states have a more normal primary election procedure, but if no candidate wins 50% in the general election, a runoff is required. Georgia’s even split between the major parties plus 2% support for the Libertarian candidate meant that the election for U.S. Senate in 2022 went to a runoff in December. In the 2020 cycle, runoffs for the U.S. Senate seats were held on January 5, 2021.

It’s important to note also that while the parties have national committees, in each state each of the major parties has an organization which is largely independent of other states and the national committee. Because all elections apart from the nomination of Presidential candidates occur at the state level, the state parties have more control over elections. In Minnesota, one of the parties even has a different name, the Democratic-Farmer-Labor party.

Presidential Nominations

The nominees for the federal presidency from the Republican and Democratic parties are chosen by delegates to the national conventions. The winning candidate must win a majority of the delegates, and multiple ballots will be cast until a candidate wins a majority. Most delegates are chosen in state primaries or caucuses. Those delegates are generally required to vote for a specific candidate on the first ballot. The national party determines how many delegates each state receives and the state party determines how the delegates are chosen. Although the voters in primaries are actually voting for delegates, the ballot normally names only the candidate for the nomination, e.g. Joe Biden, Bernie Sanders, or Amy Klobuchar. It varies whether all delegates are chosen from the slate of the candidate with a plurality of the votes (winner take all) or the delegates are assigned proportionally based on the candidates’ vote totals. The winner takes all system is more common in Republican primaries.

The primary election is a secret ballot election where you can vote absentee before election day or at any time the polls are open (usually they are open for around 12 hours) on the day of the election. A caucus system is different. For a caucus, all voters in the precinct gather at a meeting location at a specific time, usually in the evening. Iowa has used a caucus system for the presidential nominating contest in January of the election year when it is cold and it gets dark early. The voters have to sit through speeches and then divide themselves based on which candidate they support. If a candidate fails to meet a threshold of support (I remember 15%), the voters for that candidate are required to disband and choose other candidates. This requires a commitment of hours, whereas I can vote in a primary election in less than 10 minutes.

I said most delegates are chosen by primaries or caucuses because a small number of delegates become delegates by virtue of the offices they hold, whether within the party or in government. These “superdelegates” are not bound to a candidate, but they often declare their support for a candidate prior to the convention. Superdelegates are not popular with supporters of outsider candidates like Sen. Bernie Sanders because they believe superdelegates tend to support establishment candidates. The Democratic Party in particular has been pressured to reduce or eliminate superdelegates.

As to the specific points in the question:

1. In 2020, Republican parties in some states, but not all, canceled their primaries and chose delegates to the convention by some other method. I know that Wisconsin did hold a primary.
2. Prior to the 2016 Republican convention, which technically was when Trump was running against Ted Cruz et al., there was a movement to encourage delegates to violate the rules requiring them to vote for the candidate they were pledged to, and to change the rules of the convention so that the delegates were not bound.
3. Initially (say, starting 100-150 years ago) the candidates were chosen internally by the party and the general public had no way to influence what candidates appeared on the general election ballot. Because this put an important phase of the process under the control of a few people, a movement began to hold primary elections to give voters more choice. The method for choosing a nominee for U.S. President is still largely up to the party, but the major parties mainly put that decision to voters, which is how we could get a candidate who was not favored by the party establishment (Donald Trump). For offices at the state level and below, the parties may be able to get candidates on the ballot without a primary, but someone who wanted to be the nominee and was not chosen by the party might publicly complain and have the same effect that Sanders supporters may have had on the 2016 general election — at least a few Sanders supporters did not vote for Clinton because they felt the party was unfairly biased against Sanders during the primary phase. Even minor parties sometimes have primary elections, and once the party decides to have a primary, they are largely bound by state law to the choice of their voters. If the candidate dies or “voluntarily” withdraws, most states have mechanisms for party officials to substitute a candidate on the general election ballot. If the candidate is pressured to withdraw but refuses, the party is stuck. I think it’s fair to say that changes in these approaches are influenced by a combination of laws and internal party decisions.

The Presidential primary and caucus system has, perhaps only by luck, produced unambiguous results for as long as I’ve been eligible to vote. In the 1976 Republican convention, Gerald Ford was nominated on the first ballot with 52.6% of the votes, but according to Wikipedia, this result was uncertain even in the final week before the convention. I’m not aware of a subsequent convention of either major party in which the result was not known in advance. You might argue for that the 2016 Republican convention was an exception, where Trump had a clear majority of the delegates, but it was thought that bound delegates might violate their pledge to vote for Trump.

As long as this answer is, obviously it is incomplete and makes a lot of generalizations. I don’t address how minor parties get ballot access, how to get on the general election ballot as an independent, or whether you can get on the ballot as an independent after losing a party primary.

Answer 5

AFAIK these primaries are NOT part of the official electoral process in the sense that any decision that is made in primaries, by delegates or conventions or party higher ups and office holders, are MEANINGLESS.

What really matters are the ballots and ultimately the actual votes in the main election. So as sumelic has mentioned (BTW much better answer than this!) the actual question is access to the ballots. And from a rough skimming all states seem to have a process of petition and/or write-ins that allows for running a candidate outside of the party system. Often times the boundary for that is a certain amount of initial supporters, which is a box that the major parties usually already check, so that would be the party-privilege.

So why is that meaningless process relevant at all? Because it's a strategic attempt to game the "first-past-the-post"-voting system, which has the intrinsic problem of vote splitting. So to avoid that, parties make a pre-selection and then pool money, publicity and further support behind the campaign of the one singular candidate chosen in the primary. So that means a significant buff to that person's campaign and it might be hard for a candidate to run without such a support against one that has it.

So for obvious reasons it might be seen as beneficial to game that process as well and insert oneself as the leader of the operation. However the more that mandate is based on party shenanigans and the less it is a democratic mandate of the base, the more it might reveal itself that this is a very fragile house of cards. Because ultimately this is all just an in-party process which no binding authority beyond the one that people give to it. So nothing is ultimately stopping anybody from leaving that union and pooling their resources elsewhere. Depending on the structure of the party (top-down or bottom up) the access to party resources might vary so in a top-down system you might need to leave the party and/or run that in parallel while in bottom up structures you might even support them locally on the banner of the official party.

All that these primaries seek to accomplish is to present a unified monolithic front, but behind the scenes that only works if people support that and if you can't even get your own party to agree with that, then the whole purpose of this move doesn't really work.

Apparently there are still limits to the shenanigans that a party can pull, such as racist discrimination being illegal, but as I said, practically, it's an unofficial attempt to game the system, that is largely unregulated because of that, but also rather fragile because of that.