A defining feature of democracies is an independent legal system, where elites and the public alike accept the broader legitimacy of its actions, even if they run counter to political preferences. Existing scholarship suggests that public support for rule of law institutions is rooted in perceptions of procedural fairness. However, amid increasing levels of affective polarization, we posit a partisan presidential heuristic wherein citizens’ views of legal institutions are influenced by their partisanship and signals from the president. Through multiple experiments, we demonstrate that support for two key institutions—the Federal Bureau of Investigation and the Department of Justice—is substantially derived from the intersection of one’s partisan identity and their partisan proximity to the president. These effects are strongest among respondents exhibiting high levels of affective partisanship. Our results suggest that in forming perceptions of the rule of law, partisan politics is increasingly competing with perceptions of procedural fairness, thereby subverting support for legal institutions in the United States.