I was looking at the history of the political parties, and I found out that John Adams was a member of the Federalist party, while his son John Quincy Adams was a member of Thomas Jefferson's Democratic-Republican party and then switched to the National Republican party. Andrew Jackson was the first President of the Democratic party. William Henry Harrison, the first President to die in office, belonged to a party called the Whig party. The Whig party was later replaced by the Republican party. Abraham Lincoln was originally a member of the Republican party and then he switched to a temporary party called the National Union party. Andrew Johnson continued with the National Union party after Lincoln's assassination, and then switched to the Democratic party.

My question here is: What is the history behind this evolution?

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    An American history book will tell you about the evolution of the various American political party systems. Wikipedia has a lot of information. This question shows a lack of basic research.
    – Stuart F
    Nov 12, 2022 at 13:05

3 Answers 3


There is an observation among political scientists called Duverger's law. It is not a law in the sense of the laws of physics or the laws of a state, but it is a repeatedly observed pattern. Duverger found that in countries with a first-past-the-post electoral system, there tend to be only two significant parties. Periods with more than two parties are generally transition periods.

The Whigs disintegrated over the slavery issue, and according to Duverger it was natural for the non-Democrats to coalesce into a new party after a bunch of upheavals.

  • The laws of physics are literally based on repeated observations; what's the comparison here?
    – uberhaxed
    Nov 11, 2022 at 19:53
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    @uberhaxed: Soft vs hard science. If you observe one violation of a purported "law" of physics, then it's not a law anymore. If you observe Ross Perot winning a bunch of votes in the 90's, (or Theodore Roosevelt coming in second on the Progressive ticket) it doesn't invalidate Duverger's law. Duverger's law is a tendency, not an absolute.
    – Kevin
    Nov 11, 2022 at 21:59
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    @uberhaxed: Our best current models of the world all have flaws, but that doesn't mean fully accurate laws of physics don't exist. It means we don't know what they are. Nov 12, 2022 at 2:20
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    @uberhaxed: I am not going to debate philosophy of science with you in the comments section of somebody else's answer on Politics.SE. Please ask a new question on Philosophy.SE if you wish to discuss this further.
    – Kevin
    Nov 12, 2022 at 3:40
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    @uberhaxed, in politics perceptions matter. Duverger's law is being called a "law." To someone who presumably wasn't aware of it, I added the qualifier that it is a social sciences pattern, not a legal instrument or hard science. If you are not going to accept talking about these laws, would you next go complaining that a Monarch Butterfly isn't really royalty?
    – o.m.
    Nov 12, 2022 at 5:15

There are not only the reps and dems. There are other political parties.

Some other parties include the libertarians, the communists, the green party, and the democratic socialists to name just four. There are lots of other groups that are smaller and less well organized.

The reps and dems dominate because they run a system that deliberately produces this result. It is called "the two party system." There are a large number of things that are done quite explicitly to make it easier for the two main parties. This includes things like additional hurdles to get on a ballot, difficulty qualifying for tax breaks, difficulty getting included in debates, etc.

Plus, the reps and dems have party machinery that has been built up over many decades. This includes such things as political relationships among the various levels of govt (city, state, fed), relationships with members of the media, large cash reserves, contacts for mundane things like advertising, printing services, venues for various gatherings from conventions to planning sessions, etc. etc.

So how does it work? The reps and dems have a system where they get their candidates on the ballot automatically, but the libertarians or communists have to get petitions with many names. The fees are paid by the party. The party has existing advertising channels, merch suppliers, TV station buddies, etc. The reps and dems hold their debates without third parties. The party handles the legal aspects, gives their candidate the various tax break documents, and funnels party funding to their campaign. While all of that could happen for third parties, it is constrained.

So a politician with, call them "novel" ideas, finds it vastly easier to pick one of the two existing parties and work within that. So you get "wings" of the reps and dems. The social democratic wing of the dems or the libertarian wing of the reps. And this tends to syphon off people who would otherwise be in a third party. They can get party support from a large party, and get elected. Or they can struggle "in the wilderness" with a third party.

So to get a third party in requires something unusual, even extraordinary. For example, the republicans were a third party that formed over the issue of abolishing slavery.


There are some good observations from history in the previous posts, but the contemporary answer is based on two simple words, money and power. Since these two parties have been in power for a long time now, they have been able to manipulate the laws so that it is very difficult and expensive for another party to gain a foothold in the U.S. Some would say that this is the cause of the present state of polarization in the culture. For example, to be a candidate for many offices requires the gathering of thousands of signatures to be allowed to have the name printed on a ballot. For statewide races, those signatures may have to be collected throughout the state. To establish a Political Party and get candidates on the ballot is much more complex, even on a small scale... but with enough money, and lawyers that understand the process, and...and... and...

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    Money does not explain how the evolution of the political parties.
    – Arunabh
    Nov 12, 2022 at 6:00
  • While this answer could do more to detail how exactly "they have been able to manipulate the laws", one important observation might be that neither the GOP nor the Democratic party should have much interest in changing the status quo. May well be one of the underlying reasons of the law of Duverger that is briefly mentioned in the other answer. As such I find this answer useful. Nov 13, 2022 at 16:58

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