Why does the strength of local courts vary in new democracies? Highlighting empirical and theoretical puzzles generated by the state-level variation in court strength within Latin Americas two largest democracies, Brazil and Mexico, this study offers a historical institutional explanation of judicial change. Notably, in contrast to much \u27new institutionalist\u27 work — which examines the effects of formal instititutional arrangements — judicial institutions here are the dependent variable. The theoretical framework builds on existing explanations regarding the effects of electoral competition and ideology, specifying underlying causal logics and mechanisms. The framework also highlights the role of actors internal to institutions (judges), and the importance of social movement theory for understanding interactions between ideological judges and sympathetic actors outside the institution, leading to judicial mobilization or behavior \u27beyond the bench. The empirical analysis draws on the analytic leverage of a subnational level of analysis and integrates quantitative and qualitative methods, yielding conclusions that would be impossible using either method in isolation. First, time-series cross-section analyses of judicial spending (as a proxy for court strength) examine broad relationships across Brazil\u27s 26 states from 1985 to 2006 and Mexico\u27s 31 states from 1993-2007. Quantitative tools for case selection identify \u27nested\u27, model-testing cases, around which I build small-N research designs consisting of three states in each country. The in-depth, qualitative analysis draws on 115 personal, semi-structured interviews with judges and other legal elites, archival evidence, and direct observation to trace the process of judicial change. Overall, electoral competition operates as a pre-condition for reform, but its effect is indeterminate once a minimum threshold of competition is crossed. Ideology has the most consistent and meaningful effect on reform. Actors and their intentions matter. However, the expression of these intentions is contingent upon the nature of opportunity structures, including mobilization strategies and alliances, as well as overlapping historical processes. In short, I find that strong reforms are most likely where progressive judges coincide with sympathetic, left-of-center politicians. The results emphasize the role of ideas and the conditional expression of these ideas, that is, the contingency of intentionality
