Two-party system
Third parties, meaning a party other than one of the two dominant parties, are possible in two-party systems, but they are often unlikely to exert much influence by gaining control of legislatures or by winning elections. While there are occasional opinions in the media expressed about the possibility of third parties emerging in the United States, for example, political insiders such as the 1980 presidential candidate John Anderson think the chances of one appearing in the early twenty-first century is remote. A report in "The Guardian" suggested that American politics has been "stuck in a two-way fight between Republicans and Democrats" since the Civil War, and that third-party runs had little meaningful success.
New Party (United States)
The New Party was a third political party in the United States that tried to re-introduce the practice of electoral fusion. In electoral fusion, the same candidate receives nomination from more than one political party and occupies more than one ballot line. Fusion was once common in the United States but is now commonly practiced only in New York State, although it is allowed by law in seven other states. The party was active from 1992 to 1998. (There had been an earlier, unrelated New Party in 1968 that ran Eugene McCarthy for President.)