The theory of spatial voting has played a large role in the development of important results across many areas of political science. Directly testing the foundational assumptions of spatial voting theory, however, has not been possible with existing data. Using a novel survey design, this article obtains estimates of voter ideology on the same scale as candidate positions. The results of this scaling demonstrate that voters possess meaningful ideologies and, furthermore, that these beliefs are strongly related to the sorts of policy proposals considered in Congress. These ideology estimates are then used to uncover the actual relationships between ideology and vote choice for citizens of various types in the 2004 presidential election. Although the choices of independent voters are shown to be largely consistent with the assumptions of spatial voting theory, the decision rules used by partisans differ strongly from what unbiased spatial voting would imply. Although partisans do converge toward the behavior of independents, and hence toward the assumptions of spatial voting theory, as information levels increase, we see that even highly informed partisans show significant differences from what would be implied by unbiased spatial voting theory.
The fundamentals in US presidential elections: Public opinion, the economy and incumbency in the 2004 presidential election
