Scholars have consistently shown that social identities can shape political attitudes and behaviors; this article explores the reverse relationship. Are partisan identities ever strong enough to influence involvement with a politically relevant social group? Looking at an identity that has become an increasingly strong predictor of partisanship and vote choice, religion, the article develops and tests a theory that politics can affect partisans’ levels of religiosity at a certain time in their lives. An experiment and two panel studies show that when people are in the process of raising children—a time that encourages many to make decisions associated with their religious identities—their partisanship may influence these religious choices. The findings highlight politics’ role in shaping key aspects of partisans’ social identities and, ultimately, the religious makeup of the United States.