Abstract: Political scientists and legal scholars have written a good deal in recent years on the consequences of Supreme Court decisions. Much of this scholarship has been skeptical of the capacity of courts to produce significant social change. Most notably, Professor Gerald Rosenberg has declared the notion that courts can reform society a "hollow hope." While much of my own scholarship has reached conclusions broadly similar to those of Professor Rosenberg, it is a mistake to conclude that Supreme Court decisions in the civil rights context never made much difference. The Court's most important white primary decision, Smith v. Allwright, inaugurated a political revolution in the urban South. This Article considers both the circumstances that enabled Smith to accomplish what it did and the limitations of that accomplishment. My goal is to shed light on the conditions that enable and disable Supreme Court decisions from effectuating significant social change. Part I summarizes the Supreme Court's three pre-Smith white primary decisions. Part II provides legal and political background to Smith v. Allwright and also describes the post-Smith history of the white primary. Part III, the core of the Article, describes the impact of Smith on southern black voter registration. Relying principally on archival material mined from the NAACP Papers, I describe how southern blacks and whites responded to Smith and identify the political and social conditions that enabled Smith to launch a revolution in black political participation in the urban South. This Part also examines the factors that largely nullified the impact of Smith in the rural South. The Conclusion addresses the question of why the Supreme Court's intervention in the white primary context was so much more immediately efficacious than were either its contemporaneous decisions involving criminal procedure issues affecting southern blacks or its slightly later ruling in Brown v. Board of Education.