What legal impediments might there be to alternate voting systems?

Question

Most jurisdictions in the US use first-past-the-post voting. This appears to me to be a historical artifact; I'm not aware of any legal impediments on a federal level that would prevent states or municipalities from using any voting system they want, so long as it treats all votes equally. Are there any such federal restrictions of which I might be unaware?

Further, are there any state-level roadblocks? In Tennessee, where I live, I'm not aware of any legal restriction on municipalities selecting their own voting systems. Do any other states have such restrictions?

Answer 1

In the United States, most all voting law is found at the state level rather than the federal level. To that end, states are allowed to change their voting procedures as they see fit with the exception of those states, counties and municipalities that are singled out in the Voting Rights Act as needing to be pre-cleared by the Department of Justice before they can make any changes to their voting policies. These are jurisdictions that in the view of the federal government have a history of discrimination in their voting policies and can no longer be trusted to continue to change policy without approval from the federal government.

The freedom to change voting policies and systems at the state level, however, is why you see proportional distribution of electoral college votes in some states, for example. Similarly, this is why some states implement a caucus system for their primary elections, while other states prefer a straight majority vote primary system instead. Additionally, many municipalities allow voters to select multiple candidates in races for school board and city council for example, rather than selecting winners of individual races. So the ability to make those changes exist within the system at the state and local levels, but the willingness to implement changes to that system have by and large not yet arisen.

Answer 2

Are there any such federal restrictions of which I might be unaware?

Yes, Article II Section 1 Clauses 2-3 and Amendment 12 of the Constitution of United States of America.

Under the Supremacy Clause (Article VI, Clause 2) states are subordinate to Federal Law and Authority; but, where not defined, States has the right and power to determine their own laws and powers. This is the basis of "state's rights' as originally defined by James Madison in Federalist No. 44.

This means that States are constitutionally mandated to follow Article II, Section 1, Clause 3 (which defines the electoral college) and the 12th amendment (which amends the electoral college's voting process). Left at this, pursuant to state's rights, each state has the right to determine how they chose their Electors. But, Article II Section 1 Clause 2 explicitly delegates the choosing of Electors to state legislatures.

Further, are there any state-level roadblocks?

Yes; but, this varies state to state.

Voting Rights Act of 1965

As Michael noted in his answer, notably, the Voting Rights Act of 1965 explicitly regulates voting laws. Nationally, every state is prohibited from legislating racial discrimination, legislating literacy tests, and other devices historically used to discriminate against minority groups. The Act also provides "special provisions" that apply only to specified jurisdictions. In particular section 5 prohibits these jurisdictions from legislating any changes to their voter laws without preapproval from the US Attorney General or the US District court for D.C. to ensure the law will not impact protected minority groups. Furthermore, Section 4(f)(4) and Section 203(c) requires states with language minorities to provide multilingual or bilingual ballots. Note that the Voting Rights Act applies to the the states of Arizona, Texas, Alaska, Louisiana, Mississippi, Alabama, Georgia, South Carolina, and Virginia but also to ** jurisdictions**.

Resistance to Change

I don't have the time at the moment to provide cited evidence for this; but, whenever legislation is passed, it typically receives some resistance to change. Proponents of changing the voting system will receive resistance in the form of why change it? what we have already works! These opponents would provide some of your biggest roadblocks.

Municipality Level

At the municipal level, the municipality must adhere to the state legislature's laws on voting. This is why you don't see municipal level laws regarding voting.

Answer 3

I notice that the one thing that I think this question was looking for has not been mentioned yet at all: 2 USC § 2c

there shall be established by law a number of districts equal to the number of Representatives to which such State is so entitled, and Representatives shall be elected only from districts so established, no district to elect more than one Representative

This prohibits, in federal House elections (and only there), any voting system with multi-member districts. So it is an impediment to multi-member single transferable vote, as well as to statewide party-list proportional representation.

Answer 4

Single-winner plurality is not the original historical precedent in the U.S.

The original Constitution actually specifies a different method of voting for presidential elections:

The Electors shall meet in their respective States, and vote by Ballot for two Persons, of whom one at least shall not be an Inhabitant of the same State with themselves. And they shall make a List of all the Persons voted for, and of the Number of Votes for each; which List they shall sign and certify, and transmit sealed to the Seat of the Government of the United States, directed to the President of the Senate. The President of the Senate shall, in the Presence of the Senate and House of Representatives, open all the Certificates, and the Votes shall then be counted. The Person having the greatest Number of Votes shall be the President ... In every Case, after the Choice of the President, the Person having the greatest Number of Votes of the Electors shall be the Vice President. (Article II, Section 1, Clause 3)

The fact of voting for not one but two candidates in the same race (and not distinguished by ballot for different offices, but the runner-up is given the secondary office) is actually a limited form of approval voting that mitigates the spoiler effect and eliminates much of the polarization we see today from single-party tickets. This was undone and replaced with single-winner first-past-the-post plurality voting by the 12th amendment in 1804 by separating the races into distinct ballots for president and vice president. We don't even use that system today; instead our elections are administered by party-centric nominations with a single election for both president and vice president.

The momentum behind the 12th amendment and subsequent alterations to national voting system (including the popularization of state-level primaries, leveraging the Poll Tax Amendment in 1964), the nationalization of parties and their recognition in some state laws all constitute "legal impediments" to implementing alternate voting systems.

Yes, there is a restriction on the states: Elections must follow a republican form of government

The Constitution makes this stipulation which is applicable to the states in choosing their manner and mode of administering elections:

The United States shall guarantee to every State in this Union a Republican Form of Government (Article IV, Section 4)

States are free to experiment with different forms and methods of voting internally to choose their public officers and electors for national elections, but the one uniform criterion is that they must adhere to the standard of a republic. Also, for national presidential elections, only the state legislature may issue the rules governing an election (Article II, Section 1, Clause 2).