Why does the United States have a two-party political system?

Answer 1

The United States has only two major parties primarily because of the first-past-the-post electoral system. The U.S. single-member district/plurality electoral system requires a party to get a majority of the votes in a district in order to win, and the winner takes it all. Coming in second (even if only by one vote) does not count, as it would in a proportional representation system. Neither the Constitution nor state laws prohibit minor parties, nor do they mandate only two major parties. One of the criticisms of the American party system is that having only two major parties oversimplifies the electoral system, presenting voters with only two choices instead of a wide range of options. The United States has two major parties, the Democrats and the Republicans. Minor parties do exist, such as the Green Party, which is concerned with the environment, and the Reform Party, which is concerned with reforming government and paying down the national debt. However, only one "third" party in American history (the Republican Party) became strong enough to replace one of the two major parties (the Whig Party).

Answer 2

The reason is the way our electoral system is set up, in a winner take all electoral college. Third parties have garnered success, however their success leads to their demise as the ideas promoted by a third party eventually are swallowed into the platform of the remaining two.

Answer 3

There's no law that requires it, nor any reason other than that is the way it has worked out.

Additionally, there is significant institutional inertia maintaining the status quo of two parties. That is, the barriers that other parties face (in terms of gaining sufficient political support) are huge. What tends to happen is that when a significant political movement comes along in the US, rather than have a new political party created around that movement, one of the two major parties "adopts" (or more accurately, co-opts) that movement and incorporates it into that party.

The recent Tea Party movement is a good example. In many other countries, this movement would have spawned a significant political party of its own right; in the US, the Republican Party simply decided to champion many of the Tea Party causes, and thus absorbed the support for the Tea Party.

The current Winner-Take-All design of most of the US political institutions reinforces having only two major parties. In much of the rest of the world, if a party can consistently pull 20% of the vote in elections, it will generally end up with 10-20% of the power and representation. In the US, such a party ends up with 0%, as it never is able to muster 50% of the vote, and only the largest vote-getter in any election wins any representation.

Viewed from another point: with two major parties, each able to pull about 45% of the total vote, one of the two parties is pretty much guarantied to be able to pull 51% of the vote in any single election. Since there is no power to be gained by coming in second place, any party not able to pull in at least 50% of some election is shut out from power.

Answer 4

The us only has two because three is an uneven number.