Race is often identified as uniquely defining and influencing electoral processes in the United States. However, little empirical research has investigated the consequences of racial diversity for levels of voter turnout or for the nature of mobilizing institutions. On the basis of historical analyses of U.S. politics, we hypothesize that greater racial diversity is associated with lower levels of voter mobilization, weaker mobilizing institutions, and higher barriers to voter participation. Cross-sectional models for the 1950s, the 1980s, and the 1990s are tested with ordinary least squares regression techniques, using states as the unit of analysis. We find that racial diversity is a potent negative predictor of turnout levels, in each time period and in non-Southern, as well as Southern, states and that it has an especially strong relationship in presidential elections. Racial diversity is also associated nationwide with weak state and national mobilizing forces, and more difficult voter registration requirements.