This is an analysis of strategic voting under the plurality rule. Existing theories predict strict bipartism, where rational voters support only two candidates: a strict interpretation of Duvergers Law. This conclusion is rejected. The new theory employs a simple model of a three-candidate election. Unlike previous models, the level of popular support for each candidate is not commonly certain. Voters form opinions of candidate support from public and private signals. Unless knowledge of constituency-wide factors is both common and precise, there is a uniquely stable non-Duvergian equilibrium, with only partial strategic voting. Strategic voting is increasing in the precision of voter beliefs, the expected strength of a leading candidate, and the expected gap between challenging candidates. The effect of information depends critically on its source. Public signals of candidate support have a far stronger effect than privately observed signals. Surprisingly, when voting decisions are based largely on private rather than public information, strategic voting is self-attenuating rather than self-reinforcing.
