Prevailing theories of democracy focus on class conflict. In contrast, we study democratic transition when ethnic tensions are more salient than the poor/rich divide, building a model where (i) ethnic groups negotiate about allocating the economic surplus and (ii) military and political mobilizations rest on the unobserved strength of ethnic attachment. Free and fair elections elicit information and restore inter-ethnic bargaining efficiency. Autocrats can rationally choose democratic transition, even if they risk losing power, as elections reduce the opposition’s informational rent. The predictions of our framework are consistent with novel country-level and ethnic group-level panel correlational evidence on democratization in the post-decolonization period.