The Two-party System in America


By Jennifer Nicoll Victor, Ph.D.George Mason University

It is not uncommon for reformers, activists, or anyone who is dissatisfied with the current state of affairs in politics, to cast blame on America’s two-party system. After all, the partisan polarization that so strongly grips the United States today has two political parties at its roots. So, it’s not irrational to think that polarization would be disrupted if more parties were involved in politics and governing.

A poster with the images of two party nominees on it.
As parties adjust their positions and coalitions, it makes it impossible for a third party to win seats. (Image: Popular Graphic Arts – Library of Congress/Public domain)

Duverger’s Law

Despite the fact that well-intentioned reformers have generated robust third-party movements a few times in history, the lack of a permanent multiparty solution to fix problems in American politics really has nothing to do with the effectiveness of the reformers. Rather, the number of parties in any political system is determined by the electoral laws in that system.

The 20th-century French political scientist Maurice Duverger generated what today is called ‘Duverger’s Law’ to explain this phenomenon. Duverger’s Law says that any system that is characterized by single-member districts and plurality election rules will naturally tend to have two, and only two, political parties.

In the United States, people are elected to the House of Representatives in individual districts. Each congressional district has one and only one representative. This means that the US Congress has single-member districts. Also, representatives are elected to Congress in elections where whichever candidate gets the most votes is the candidate that wins. This is known as a plurality rule.

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Impossible for a Third Party to Win Seats

The reason these electoral rules tend to produce only two political parties is that in this type of system, when a third party arises to challenge the two existing parties, the existing parties have an incentive to adjust their stance or position such that the people who would be attracted to the third party, ultimately find one of the existing parties to be palatable.

As parties adjust their positions and coalitions to make themselves as attractive as possible to the broadest portion of the population, it makes it almost impossible for the third party to win seats. Notably, Duverger’s Law says nothing about which two political parties will exist, only that under electoral systems like the one in the US, two political parties are the most likely outcome.

Learn more about the history of political parties in the United States.

The Six Party Systems

The history of America’s political parties is broken down into six periods or ‘party systems’. The two political parties that are seen today, namely the Republicans and the Democrats, can be traced back to the third party system, from 1860 until 1896, during the Civil War and the period of national Reconstruction that followed it. This new party system developed because voters and electoral coalitions realigned themselves into new groups with new names.

It was during the third party system that the two major parties, Republicans and Democrats, first emerged and these are the names that they have been using ever since. However, the make-up of these coalitions has changed drastically over the years. During the third party system, the Republican Party was primarily an anti-slavery party.

Republicans and Democrats in the Third-party System

The Republican Party of the 1860s was also relatively protectionist when it came to foreign affairs, meaning that they advocated shielding domestic industries through tariffs on foreign imports. The party was strongly geographically regional, existing primarily in the northern part of the country. Republicans then believed in government regulation of the economy in a way that is similar to modern-day Democrats.

In opposition, the Democratic Party of the 1860s was the pro-slavery party. And, like the Republicans, the Democrats were geographically concentrated, primarily in the southern part of the United States.

During the Civil War, the difference between Republicans and Democrats was largely over the all-important issue of slavery.

Democrats Lead in the Fifth Party System

During the third and fourth party systems, Republicans remained strong and were the dominant party.

The tables turned and the Democrats became the more dominant party only during the fifth party system when they had a virtual turnaround in terms of their stand vis-à-vis the African American population.

It was then that the Democratic candidate for president, John F. Kennedy, calculated that if Democrats embraced the enfranchisement of African Americans in the south, the party could expand its coalition in a way that would provide an advantage to northern liberals.

Interestingly, during this time, ideology and political party were not as aligned as they are today. The Democratic coalition was made up of northerners and conservative southerners, and the Republican coalition was made up of conservative northerners.

Enfranchisement of African Americans

Lyndon Johnson and Martin Luther King, Jr. shaking hands after the signing of the Voting Rights Act.
It was under a Democratic president that the Civil Rights Act and the Voting Rights Act were passed. (Image: Yoichi Okamoto/Public domain)

In retrospect, it seems like the Republican Party could have moved first to enfranchise African Americans and expand their voting coalition in the south, but the Democrats beat them to it.

It was under a Democratic president that the Civil Rights Act and the Voting Rights Act were passed in 1964 and 1965, setting up a virtual marriage of political loyalty between Democrats and African Americans that still persists today.

Learn more about how Congressional elections work.

Republicans and Democrats Today

The sixth party system began around 1968 with the election of Richard Nixon and continues into the beginning of the 21st century. The contemporary Democratic coalition maintains support among union workers and middle-class intellectuals and professionals.

Republicans, on the other hand, coalesce around ideas about personal liberty, the value and strength of the free-market economy, and religious conservativism. The Republican Party has effectively appealed to disaffected social conservatives in the south who no longer felt comfortable in the Democratic Party as it embraced civil rights and racial quality.

Thus, by the end of the sixth party system, the two parties, Republican and Democrat emerge in near-perfect alignment between ideology and political parties, miles away from where their political journeys began.

Common Questions about the Two-party System

Q: In the 1860s, how was the Republican Party similar to the modern-day Democrats?

Republicans and Democrats first emerged during the third party system. The Republican Party of the 1860s believed in government regulation of the economy in a way that made it similar to modern-day Democrats.

Q: During the Civil War, what was the difference between Republicans and Democrats?

The difference between Republicans and Democrats was largely over the issue of slavery. The Democratic party of the 1860s was the pro-slavery party whereas the Republican Party was primarily anti-slavery.

Q: When were the Civil Rights Act and the Voting Rights Act passed?

It was under a Democratic president that the Civil Rights Act and the Voting Rights Act were passed in 1964 and 1965.

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