Despite the prominence of ideology in both the political science literature and everyday discourse about politics, the measurement of ideology remains a relatively underdeveloped area of research. Political scientists have agonized over finding the best methods to measure things such as political sophistication (Luskin 1987; Delli Carpini and Keeter 1993) and racial resentment (Kinder and Sears 1981; Sniderman and Carmines 1997), but more often than not they seem content to use a simple, seven-point self-placement questionaire to measure the entirety of people's political ideology. This seems particularly odd given the status of ideology as a central variable in many political science theories.

The detection and measurement of ideology are important for the study of spatial voting because the theory assumes that ideology, or, more specifically, a voter's ideological proximity to the positions of candidates, is the central determinant of their vote choice. Therefore, empirically testing spatial theory requires accurate measurements of the ideology of voters on the same scale as the positions of candidates in a given election. This requirement has not been easily met in past studies, which have often relied on less-than-ideal data sources accompanied by strong assumptions in order to produce the ideology measures required for such investigations.