Why are there only the Democratic party and the Republican party currently in the US?

Question

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?

Answer 1

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.

Answer 2

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.

Answer 3

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...