We present a theory of identity politics that builds on two ideas. First, voters identify with the social group whose interests are closest to theirs and that features the strongest policy con.ict with outgroups. Second, identification causes voters to slant their beliefs toward the group.s distinctive opinion. The theory yields two main implications: i) voters.beliefs are polarized and distorted along group boundaries; ii) economic shocks that induce new cleavages to emerge also bring about large changes in beliefs and preferences across many policy issues. In particular, exposure to globalization or cultural changes may induce voters to switch identities, dampening their demand for redistribution and exacerbating con.icts in other social dimensions. We show that survey evidence is consistent with these implications.