This book is about the policy views of ordinary Americans and how these views relate to the choices they make in elections. More fundamentally, it is about how well the political behavior of voters can be described by a simple formalized theory called spatial voting.

Early on in my political science training, I was struck by what I viewed as a large disconnect in the way political scientists thought about voters. On the one hand, many theories dealing with the behavior of candidates, members of Congress, or others abstracted away voter behavior, either explicitly or implicitly, as conforming to some simple decision-making rule. Most commonly, it was assumed or implied that voters cast their ballots for the candidate who was closest to them in some ideological space. By contrast, the empirical political behavior literature spent much of its time chronicling the idiosyncrasies and overall lack of political competence among the vast majority of voters, often concluding that the electorate was incapable of making reasoned choices based on ideological concerns. The stark contrast between these two views struck me as fundamentally problematic. Either most of mainstream political behavior was ignoring a simple, direct, and elegant explanation of voting or much of the existing theory about the behavior of candidates and elected officials rested on unsound foundations.

My initial efforts to investigate these ideas came up against a significant stumbling block. Testing spatial theories of voting would require knowing the ideological positions of voters and candidates for office on the same ideological scale.