A Common-Space Measure of State Supreme Court Ideology

bonica, adam ; woodruff, michael j.;

We introduce a new method to measure the ideology of state Supreme Court
justices using campaign finance records. In addition to recovering ideal point
estimates for both incumbent and challenger candidates in judicial elections,
the method�s unified estimation framework recovers judicial ideal points in a
common ideological space with a diverse set of candidates for state and federal
office, thus facilitating comparisons across states and institutions. After discussing
the methodology and establishing measure validity, we present results for
state supreme courts from the early 1990s onward. We find that the ideological
preferences of justices play an important role in explaining state Supreme Court
decision-making. We then demonstrate the greatly improved empirical tractability
for testing separation-of-powers models of state judicial, legislative, and executive
officials with an illustrative example from a recent political battle in
Wisconsin that ensnared all three branches.