© 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group. How do voters’ identities change after a candidate’s defeat? A longitudinal, within-subjects study used Hillary Clinton’s loss in the 2016 U.S. presidential election to explore social identity theory’s (SIT) tenet that threats to self-relevant groups motivate further connection to and affirmation of the group. Two independent samples (university students and adults on Mechanical Turk) were assessed before and after the 2016 U.S. presidential election. After Hillary Clinton’s defeat, those who reported voting for Clinton affirmed their political and gender identities in several ways, such as increasing their identification with Clinton. These ecologically valid results are consistent with SIT, and suggest supporters affirm their identities following a threat such as the defeat of their candidate during a high-stakes election. We discuss the implications of these findings within the context of the increasingly polarized U.S. electorate.