Does State Political Ideology Change over Time?

Students of politics in the American states agree that political ideology varies significantly between the states. Due to the path-breaking work of Wright, Erikson and McIver (1985) and their subsequent research, there is consensus that interstate differences in public ideology are important in accounting for notable differences among the states in the policies they adopt. Despite this consensus, however, there remains a fundamental debate among state politics researchers regarding whether public ideology changes within the states in the post-WW II era. Erikson, Wright, and McIver (1993) contend that state-level ideology is mostly stable, with over-time variations representing “noise.” Alternatively, Berry, Ringquist, Fording, and Hanson (1998) argue that meaningful ideological change occurs within states over time. We test the hypothesis that ideology is stable at the state level. In addition to using the data developed by these teams of researchers, we construct an alternative data set to provide an out-of-sample test of their conflicting expectations. The results have significant implications for the study of state political processes. Systematic analysis underscores the stability and relative dominance of between-state differences indicating that the effects of ideology commonly observed in many state policy studies are due to interstate variation rather than temporal change. However, we also find note-worthy longitudinal ideological variation within selected states during the last three decades. Scholars interested in studying the causes and consequences of state-level political ideology—particularly their implications for public policy adoption and change—might profitably focus on the handful of states where survey-based measures indicate the presence of ideological change.