Political expression often revolves around ethnic, religious, or cultural group identities. I develop a game-theoretic model explaining how group identities interact with citizens' social environments to induce political behavior designed to express group identity. Citizens make political choices before engaging in social interactions which may involve members of the individual's ingroup or outgroup. The strength of an individual's group identity is private information and affects payoffs from political behavior and from cooperative behavior in social interactions. Therefore, symbolic political behavior informs social interactions by revealing information about the group identity of the participant. Furthermore, cross-cutting pressures from ingroup and outgroup interactions govern the intensity with which individuals pursue symbolic political behavior. Symbolic political behavior is more common in segregated communities and among members of large majority groups. I illustrate the broad importance of the theory through applications to anti-immigrant activism.