Although the United States allows for multiple political parties, two major parties — the Democratic Party and the Republican Party — have dominated the political landscape since the mid-1800s. This phenomenon is known as a two-party system, and it shapes nearly every aspect of American elections, policymaking, and governance.
The Democratic Party was founded in the early 19th century, while the Republican Party was established in 1854. Since then, all U.S. presidents have been members of either of these two parties. The last time a president from a different party was elected was in the 1850s, with Millard Fillmore from the Whig Party.
Several factors contribute to this enduring dominance. One key reason is the winner-take-all electoral system used in most U.S. elections. Unlike proportional representation systems used in other democracies, where multiple parties can win seats based on vote share, American elections usually award victory to the candidate who gets the most votes — even if it’s not a majority. This discourages support for smaller parties, as voters often fear “wasting” their vote.
Another reason is ballot access laws. It is often costly and complicated for third-party candidates to get on the ballot in all 50 states. In contrast, Democrats and Republicans are automatically included due to their established status.
The two-party system also benefits from media coverage, political funding, and institutional support, which typically favor the major parties. Most debates, especially presidential ones, exclude third-party candidates unless they meet strict polling thresholds.
While third parties like the Libertarian Party or Green Party exist and sometimes influence public discourse, they rarely win major offices. As a result, U.S. politics continues to be a contest primarily between the two dominant forces — Democrats and Republicans — shaping national policy and public debate for over 150 years.