Political science generally treats identities such as ethnicity, religion, and sexuality as “unmoved movers” in the chain of causality. I hypothesize that the growing salience of partisanship and ideology as social identities in the United States, combined with the increasing demographic distinctiveness of the nation's two political coalitions, is leading some Americans to engage in a self‐categorization and depersonalization process in which they shift their identities toward the demographic prototypes of their political groups. Analyses of a representative panel data set that tracks identities and political affiliations over a 4‐year span confirm that small but significant shares of Americans engage in identity switching regarding ethnicity, religion, sexual orientation, and class that is predicted by partisanship and ideology in their pasts, bringing their identities into alignment with their politics. These findings enrich and complicate our understanding of the relationship between identity and politics and suggest caution in treating identities as unchanging phenomena.