Why does America have only two parties? We usually hear it’s because of the voting system. Proportional representation (PR) causes more than two parties. And until the United States has proportional representation, you’d better not vote for third parties!
Not so much.
The United States has only two parties because those are all people vote for.
Why it’s not the lack of PR
Every published study on the adoption of PR voting agrees. Sitting politicians enact PR after the number of parties has grown. Examples: Ahmed (2015), Blais et al (2005), Blais and coauthors (2008), Boix (1999), Calvo (2009), Colomer (2005), Cusack et al (2007), Leeman and Mares (2014), Pilon (2013), Renwick (2011), Shugart, Wattenberg, and coauthors (2003). I’m sure there are others. You get the point.
Even in the United States, moves to PR did not precede change in party systems. American cities adopted PR after a local major party had factionalized — that is, given way to a de facto multi-party system.
How can it be true that we don’t have more parties because we don’t have PR — if the onset of more parties causes PR? It cannot.
Why it’s not presidentialism
Many countries with more than two parties have the same system as us. Canada. India. The United Kingdom. All first-past-the-post. Why more parties in them?
You might think it is parliamentarism. In a parliamentary system, there is no need to worry about electing a president. Voters pick parties, and parties pick the prime minister. That means you don’t need to funnel all voters into two camps. In the United States, however, you do.
South America has nine pure presidential systems. Each of them has more than two parties. How, then, do they end up with presidents? The same way that parties agree on prime ministers. They make deals.
Well, it must be the Electoral College
True, it hurts when third parties spoil the vote in a pivotal state.
But I see no reason why parties in the United States cannot do what parties in South America do: make deals. Might it be messy? Sure. Might voters decide they don’t like the deal? Sure. But the possibility of pre-election deal-making within the Electoral College framework means that the Electoral College alone cannot explain the number of parties.
As a matter of fact, U.S. presidents once won office in the South American way. In the 1930s, the American Labor Party would tell its supporters to vote for Franklin D. Roosevelt. It would not run its own candidate. At the same time, it would do its own thing in state and local politics (including the federal Congress).
What about primaries?
Some argue that the widespread use of primary elections makes our two parties penetrable by groups that, in other systems, might emerge as third parties. This makes sense, but two points are in order.
Third-party voting in House and gubernatorial elections spiked after the turn to primaries. It then fell in the 1940s. Why might that be?
As it turns out, primaries are hard to contest. Recent work on presidential voting, Congressional primaries, and state parties all argue that party insiders dictate the outcomes of primaries. It may be that persistent third-party voting grew out of trouble in primaries.
Incidentally, I keep turning up evidence that trouble in primaries was one reason for the turn to PR in some cities. In Cincinnati, for example, labor unions in 1924 accused the Republican Party of rigging the local primaries. And when analyzing data from Worcester, Mass., I found that the precincts most supportive of a 1947 PR ballot measure were those that had seen the most hotly contested Democratic primaries one month before.
What flattened third-party voting was the New Deal consensus. Third-party voting was higher than now for most of American history. After the New Deal, in national politics at least, farmers and workers had no further need to vote for third parties.
So, the reason for only two parties is that we inhabit a rare period in American history. Whether it will persist is anyone’s guess.