Government » American Political Parties » The Two-Party System

Summary and Main Ideas


Electoral rules, such as the use of plurality voting, have helped turn the United States into a two-party system dominated by the Republicans and the Democrats. Several minor parties have attempted to challenge the status quo, but usually they have only been spoilers that served to divide party coalitions. But this doesn’t mean the party system has always been stable; party coalitions have shifted several times in the past two hundred years.

Practice Questions

  1. What impact, if any, do third parties typically have on U.S. elections?
  2. In what ways do political parties collude with state and local government to prevent the rise of new parties?

Sample Answer:

1. Third parties bring important issues to the attention of the major parties. They also often serve as spoilers in the elections they enter.


critical election: an election that represents a sudden, clear, and long-term shift in voter allegiances

first-past-the-post: a system in which the winner of an election is the candidate who wins the greatest number of votes cast, also known as plurality voting

majoritarian voting: a type of election in which the winning candidate must receive at least 50 percent of the votes, even if a run-off election is required

party realignment: a shifting of party alliances within the electorate

plurality voting: the election rule by which the candidate with the most votes wins, regardless of vote share

proportional representation: a party-based election rule in which the number of seats a party receives is a function of the share of votes it receives in an election

two-party system: a system in which two major parties win all or almost all elections

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