What motivated Trump Supporters to storm the US Capitol in protest of the US Election results? We examined how different dimensions of an identification (Trump, Republican) predicted intentions to engage in activism or radicalism in the wake of the 2020 US Presidential Election. We sampled self‐identified Republicans 3 weeks before (N = 273), and 10 days after (N = 277), the US Capitol Insurrection. We separately measured identification as a Republican and Trump Supporter before assessing people's perception that the 2020 Election was illegitimate. We then assessed two emotions (anger, contempt) and two forms of collective action intentions (activism, radicalism). Both studies showed that stronger Trump identification, but weaker Republican identification, predicted perceptions that the 2020 US Election was illegitimate. Perceptions of illegitimacy predicted feelings of anger and contempt, which differently predicted normative and nonnormative collective action. Results suggest that different dimensions of identification predispose people to different perceptions of events and, consequently, harbor different action intentions.