The Impact of Judicial Selection Method on State Supreme Court Justice Ideology

Among political institutions in the United States, state courts are surprisingly susceptible to ideological extremism because of the non-uniform ways judges are selected. In this paper we examine the effect of selection methods on the ideological composition of state supreme courts. We theorize that methods involving partisan politics lead to more ideological justices and that, among that subset, Republican affiliated justices will be the most extreme. We test our expectations using a dataset of over 600 state supreme court selections between 1961–2011. Using a contemporary matching algorithm designed to maximize causal identification, we find support for our hypotheses. Our results speak to the consequences of federalism in court composition and offer an insight into how polarization manifests in the judiciary.