Chapter 44: Why Do We Have a Two-Party System?

“In our view, the ideal of popular sovereignty plays much the same role in contemporary democratic ideology that the divine right of kings played in the monarchical era. It is . . . a fiction providing legitimacy and stability to political systems whose actual workings are manifestly—and inevitably—rather less than divine.”

—Christopher Achen and Larry Bartels (1)

A Two-Party System and Its Alternatives

Since the Republican Party’s rise in the 1850s, all American presidents have been either Democrats or Republicans. The vast majority of congressmen since then have been either Democrats or Republicans. Because of the two major parties’ dominance, political scientists classify the United States as a two-party system, even though we have many political parties. A two-party system is distinct from its alternatives: a one-party system in which other parties are either banned or so hobbled that they can’t compete with the ruling party, or a multi-party system, which features three or more parties with a viable shot of participating in government. Modern history is full of one-party political systems like Nazi Germany and the Soviet Union. Iraq under Saddam Hussein was a one-party system. The People’s Republic of China is a one-party system. One-party systems can also be found in North Korea, Vietnam, and Cuba. Multi-party systems exist in many countries like Denmark, France, the United Kingdom, Germany, Australia, and New Zealand. Why is the United States a two-party system as opposed to a multi-party one? It is, after all, a very diverse country that could probably support more than two parties.

Causes of America’s Two-Party System

The consensus among political scientists is that two structural features strongly favor a two-party system as opposed to a multi-party system. The first consists of a variety of laws that limit ballot access and otherwise penalize third parties. For instance, congressional rules all favor the Democrats and Republicans. If someone from a third party or a person with no party affiliation is elected to Congress, she must choose to be affiliated with one of the major parties to get assignments to standing committees. Presidential candidates from the major parties receive public money to run their campaigns. But when a third-party candidate runs for president and wants public funding through the FEC, she has to receive that funding after the election is over because the amount is tied to how well they did in the last election.

Third parties complain loudest about ballot-access restrictions, which are any barriers to getting a candidate on the ballot so voters don’t have to write in their name. They argue that were today’s ballot-access restrictions in place in the 1850s, the Republican Party never would have risen to become a national party. As political analyst Richard Winger points out, the first ballot-access restrictions began in the late 1880s and became progressively stricter in the 1930s and the 1960s. (2) Natural experiments have shown that when ballot-access restrictions were lowered, the major parties faced significantly increased competition from third party and independent candidates. (3)

Ballot-access restrictions include filing fees, early deadlines to declare candidacy, and signature requirements. The latter is perhaps the most onerous burden on third parties. Many states require independent and third-party candidates to secure enough signatures on petitions in order to get on the ballot. Simply put, “The greater the share of the electorate required to sign nominating petitions, the fewer minor-party and independent candidates appear on the ballot.” (4) A third party that wants to run candidates for all the House seats across the country would have to collect millions of signatures. The Democrats and Republicans are relieved of this burden. Collecting these signatures is expensive and time-consuming. Together, filing fees and signature requirements stunt electoral competition, especially races for the House of Representatives. (5)

The second structural element causing the United States to have a two-party system is our winner-take-all elections—which the British refer to as a first-past-the-post system—used in single-member districts. In such a system, a single person represents each electoral district for the House or Senate and gets that distinction by receiving the most votes of those cast, even if he did not receive the majority of the votes. So, if Bill receives 546 votes, Mary receives 545 votes, and Sam receives 544 votes in a U. S. House of Representatives’ election, Bill wins even though he received only 33 percent of the vote. He received the most votes short of a majority, called the plurality of votes, and he will represent that district. Coming in second gets Mary nothing, and Sam is similarly out of luck even though he received only 2 votes less than the winner. The tendency for winner-take-all, single-member district systems to promote two parties is sometimes referred to as Duverger’s Law, after the French political scientist Maurice Duverger.

How does the winner-take-all system help create a two-party system? To answer that, we’re going to need a more realistic example. Let’s say we have a liberal party that pushes the interests of the common laborer but has also been somewhat environmentally friendly—the Blue Party, and we have a conservative party that pushes the interests of big business and entrepreneurs and is very unfriendly to the environment—the Red Party, and we have a new party that is very concerned about the environment—the Green Party. Let’s assume we have three election districts, and the Green party starts strongest in one region. Finally, let’s be realistic and say that the Green Party does not have the strength that third-place winner Sam did in our example above. We have an election, and these are the results:

Hypothetical election between Blue, Green, and Red parties.What happened? Blue wins two seats by getting the plurality of votes in District One and the majority of votes in District Three. Red wins one seat in District Two. Green gets nothing, bupkisnichtsnada. And this is after the Greens have gone through all the work and expense of getting the party started and getting on the ballot. Can the Green devotees keep the party going for two years until the next election? Maybe. Let’s assume that not only do they keep it going, they actually do a little better. Here are the results for the next election two years later:

Hypothetical election between Red, Green, and Blue parties.Indeed, the Greens did a bit better, but what did it get them? Still nothing. The first lesson from this is that it’s very difficult to keep a new party going year after year if all that effort is not producing actual legislative seats. In this case, the Green party saw tremendous gains for a third party. That’s often not the case, and so aside from keeping the party going, it becomes difficult to convince citizens to keep voting for a loser that has little chance of gaining seats in Congress. People want to vote for a party that stands at least some chance of winning seats. That’s the second lesson. The third lesson is equally important. Look what happened in that second election. Green pulled voters away from Blue, which is the second choice among eco-voters because it is at least somewhat environmentally friendly. By doing so, these voters hurt the Blue party and guaranteed that Red would pick up another seat even though Red’s support didn’t actually go up. Since the average Green voter despises the Red party program, their support for the Green party in the election booth has led to the perverse result of having helped Red carry out its antienvironment program. In District One during Election #2, the Green candidate was the so-called spoiler candidate, who pulled enough votes away from the Blue candidate to ensure that Red won the seat.

What is a Green voter to do? One choice is to keep voting Green with the hope that the Blue party will self-destruct so that the Greens will be the only real alternative to the Reds. Something like that hasn’t happened in the United States since the 1850s, so its likelihood is not high. Still, some people make this choice on principle. Many others, however, tend to stay within the Blue party and work to make it more environmentally friendly, which deprives the Green party of activists and undercuts the distinctive Green party call among the broader electorate.

What If?

What if we required third parties to gain enough signatures in a state once, after which they would be guaranteed ballot access in perpetuity instead of having to do it each election? In addition to that change, what if we also took a different approach to voting? One approach might be ranked choice voting (RCV), which has voters ranking all the candidates—e.g., I prefer Samantha first, José second, Bill third, and Kendra fourth. Votes are then counted in rounds. When RCV is used for single-winner districts, it goes like this: Someone can win an outright majority on the first round, and she is elected. If no candidate wins an outright majority on the first round, the candidate with the fewest votes is eliminated, and that candidate’s voters—who picked her as their first choice—will have their second-ranked choice votes allocated. This process continues until someone gets an outright majority of votes. RCV would work in a similar fashion for election districts with more than one winner. (6) RCV could easily be combined with multi-member districts, which might give more people the feeling that they are not wasting their vote.


  1. Christopher H. Achen and Larry M. Bartels, Democracy For Realists: Why Elections Do Not Produce Responsive Government. Princeton: Princeton University Press, 2016. Page 19.
  2. See Richard Winger, editor of Ballot Access News, “The Importance of Ballot Access,” archived here. Richard Winger, “Institutional Obstacles to a Multiparty System,” in Paul S. Herrnson and John C. Green, editors, Multiparty Politics in America. Lanham, MD: Rowman and Littlefield, 1997.
  3. Marcus Drometer and Johannes Rincke, “The Impact of Ballot Access Restrictions on Electoral Competition: Evidence from a Natural Experiment,” Public Choice. September 25, 2008. Pages 461-474.
  4. Barry C. Burden, “Ballot Regulations and Multiparty Politics in the States,” PS: Political Science and Politics. October, 2007. Page 671.
  5. Stephen Ansolabehere and Alan Gerber, “The Effects of Filing Fees and Petition Requirements on U.S. House Elections,” Legislative Studies Quarterly. 21(2). May 2, 1996.
  6. See: FairvoteRanked Choice Voting Resource Center.




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