In this study, I have sought to identify conditions that influence the probability of the Supreme Court successfully exercising judicial power by causing the behavior of relevant actors to conform to its preferences as expressed in its rulings. My study has identified two factors that influence whether or not the Court successfully alters behavior through its rulings: the institutional position of those responsible for implementing the decision and the popularity of the decision. The Court tends to succeed at exercising power when it issues rulings in vertical issues (those in which lower courts can directly implement the decision) or popular rulings in lateral issues (all other issue areas); however, the Court tends to fail at exercising power when it issues unpopular rulings in lateral issues. Throughout the study, I have taken great care to avoid some of the methodological problems that have hampered previous examinations of Supreme Court power. I summarize my findings in Table 8.1.