This article is a first attempt to develop and assess the competing predictions of the thermostatic model of public opinion and legitimation theory for the responses of public mood to Supreme Court decisions. While the thermostatic model predicts a negative relationship between the ideological direction of Supreme Court decisions and changes in public mood, legitimation theory predicts that changes in mood should be positively associated with the ideological content of the Court's actions. I assess these rival expectations by modeling the dynamic relationship between mood and cumulative judicial liberalism. The model estimates indicate a complex interaction between the Court and the mass public characterized by short-term backlash against Supreme Court decisions in mood followed by long-run movement toward the ideological positions taken by the Court. The results emphasize the legitimacy of the Court in American politics and point to a unique role for the Court in shaping public opinion.