This paper examines the expanded role of the U.S. Supreme Court in interpreting the Constitution and striking down laws as unconstitutional in the twentieth century. It situates this transformation of the Court in the broader political environment within which the Court operates and argues that the Court's expanded role has been staunchly defended and encouraged by powerful political actors and that the Court has been careful to operate within the bounds of expected political support. In particular, the conservative wing of the Republican Party was instrumental in defending the Court and judicial review as essential institutions within American constitutionalism against progressive challenges in the early twentieth century, forcing progressives to abandon their initial hostility to judicial review as contrary to popular government in favor of a new emphasis on the ultimate consistency between democracy and an appropriately active Court. As Robert Dahl expected, the Supreme Court has not been actively countermajoritarian, but contrary to his expectations this has still been consistent with a constitutionally active Court.