How do citizens form perceptions about the ideological priorities of insulated institutions? Currently, there is little consensus on how or even whether citizens form such views. Focusing on the Supreme Court, I argue that perceptions of institutional ideology are influenced by an inter-institutional heuristic, or the popular perception that the president directly and indirectly influences the Court’s ideological direction. Using a multiple method approach, I demonstrate that citizens perceive the Court’s preferences to coincide with the president’s, changing predictably in the aggregate and varying substantially at the micro-level. The findings speak to debates about polarization in politics, showing that citizens may perceive insulated institutions as ideologically extreme due to factors beyond their control.