The number of Americans with no religious identification has grown to nearly a quarter of the population in 2018. What are the political implications of this cultural change? Current research views religious disaffiliation as an example of either backlash to the religious right (expecting the unaffiliated to be engaged partisans) or drift from institutions (expecting them to be disengaged from politics). I address this debate with three studies that examine political engagement, opinion formation, and organized advocacy among the nonreligious. Across all three studies, theories from cultural sociology suggest that simple categorical measures of nonreligious identity hide substantive differences in how people engage nonreligion in their personal lives (through low religious practice, non-belief, and nonreligious identification) and in public life (through opposition to religious authority in the public sphere). For engagement, new analysis with existing survey data with validated voter turnout shows that classic measures of low church attendance associate with higher odds of turnout among unaffiliated respondents. For opinion, analysis of original survey data shows that measures of public nonreligion are more closely associated with progressive political views than measures of personal nonreligion. For advocacy, analysis of tax and lobbying records of forty nonreligious organizations shows how a focus on personal nonreligious identities creates a closed network of groups with a more narrow agenda than organizations lobbying for the separation of church and state. By focusing on the substantive differences between cultural repertoires of personal and public nonreligion, I highlight how public religious considerations are an important explanatory factor in political life. Slippage between these repertoires can explain why the nonreligious appear to have large political potential, but limited political impact.