Does your ethnic identity change because of politics? New research suggests identities are not fixed but can be reshaped by partisan alignment. Using a 4-year panel dataset, this study finds that political partisans actively shift their self-perceptions to align with group stereotypes as the nation's two coalitions become increasingly distinct along demographic lines. Key findings reveal ethnicity and religion switching tied directly to past partisan identification. This challenges long-held assumptions about identity stability and shows how politics can reshape fundamental aspects of social self-categorization.