What role do third parties play in the U.S. political system?

Barriers to third-party success: Although the Constitution doesn’t make any rules about political parties, US government has a two-party system in which candidates from the two major political parties win nearly all elected offices. Many third parties have emerged over time, but two major barriers have prevented third parties from electing many candidates. First, most US elections operate by the winner-take-all system, which awards seats only to the candidate or party who wins the most votes in an election; independent or third-party candidates, who have neither the name recognition nor the organizational support provided by the major parties, rarely win the majority of votes. Second, the two major parties frequently incorporate the platforms of third parties into their own platforms; voters who identified with a third-party issue will often vote for a major party candidate who has adopted that issue because major parties are more likely to succeed.