In this dissertation I develop and test a theory of legal change that views the U.S. Supreme Court as operating within a complex legal and political framework. I argue that the Court uses the process by which it decides cases as an institutional tool, allowing it to exert influence in the broader political and legal environment. The Court does this by allocating agenda space to specific types of issues over others, and also by articulating legal doctrine in its written opinions that helps to shape outcomes outside of the immediate case. I test the implications of this theory in the context of both the Court's agenda setting and its written opinions. I find evidence of influence in these contexts not only from the justices but also from a variety of policy entrepreneurs that have a stake in the outcomes on the Court.