How does social exclusion on the basis of racial/ethnic identity affect partisanship and political attitudes? Drawing on sociological research on the group basis of partisanship and psychological theories of social identity, we contend that exclusion at the individual level stemming from racial/ethnic group membership can affect political identity. People who feel that a political party excludes them from the American social fabric based on their race/ethnicity should be less likely to perceive that party as serving their group’s interests and therefore less likely to support that party. We apply our theory to Asian Americans, an understudied minority population that is becoming increasingly politically relevant. Through both a large-scale, representative survey and a novel laboratory experiment, we find empirical support for our principal hypothesis. Our findings partly explain why Asian Americans are overwhelmingly likely to identify as Democrats and advance an identity-oriented explanation of partisanship in American electoral politics.