Anticipating Entry: Major Party Positioning and Third Party Threat

Observers of U.S. elections have reason to believe that third parties are not relevant political actors since they rarely win many votes or influence which major party wins an election. Researchers should use dependent variables besides vote choice and vote share to find third party effects that are a normal aspect of the American two-party system. A spatial model of elections motivates the hypothesis that a higher likelihood of third party entry induces greater major party candidate divergence. An empirical test that uses candidate positioning data in the 1996 U.S. House elections provides evidence of this third party effect.