Protest campaign movements are often carried out by coalitions rather than by homogeneous groups. Accordingly, an opposition member has both a narrow partisan identity and a broad all-opposition identity. Seeking to prevent mass political participation, autocracies can repress protesters regardless of their group membership or apply the “divide and conquer” principle, targeting specific groups. Any strategy of repression drives some dynamics of identity. For instance, broad repression may rally the opposition by increasing broad identity at the expense of narrow identity. This dynamic of identity causes complex dynamics of motivation for participation in the protest, which affects the turnout. The paper introduces a computational model to describe the dynamics of the turnout. The model employs the social identity model of collective action (SIMCA) and accounts for the dual protest identity.