Berry, William, Evan Ringquist, Richard Fording and Russell Hanson. “Measuring Citizen and Government Ideology in the American States, 1960-1993.” American Journal of Political Science, 42 (January 1998): 327-48.

We construct dynamic measures of the ideology of a state's citizens and political leaders, using the roll call voting scores of state congressional delegations, the outcomes of congressional elections, the partisan division of state legislatures, the party of the governor, and various assumptions regarding voters and state political elites. We establish the utility of our indicators for 1960-93 by (i) examining and, whenever possible, testing the assumptions on which they are based, (ii) assessing their reliability, (iii) assessing their convergent validity by correlating them with other ideology indicators, and (iv) appraising their construct validity by analyzing their predictive power within multivariate models from some of the best recent research in the state politics field. Strongly supportive results from each battery of tests indicate the validity of our annual, state-level measures of citizen and government ideology. Substantively, our measures reveal more temporal variation in state citizen ideology than is generally recognized.