Publication Type: Conference Paper/Unpublished Manuscript Review Method: Peer Reviewed Abstract: I examine the affective and cognitive aspects of party identification with new measures that capture feelings and thoughts about being a partisan, rather than measuring evaluations of or emotions felt about a party. Distinctions are made between Democratic and Republican group identities through analyses of three dimensions of identity (cognitive centrality, ingroup affect, and ingroup ties; Cameron 2004). Social Identity Theory provides a framework in which I test hypotheses about the influence of those dimensions on political attitudes and behavior. A statewide 2007 survey of registered voters in California included questions designed expressly for this purpose. Among Republicans but not Democrats, partisan attitudes about elected officials were explained by ingroup ties--the bond one feels with other ingroup members. Partisan vote choices were explained by ingroup affect--the feelings one has about being a member of the group. This effect was stronger among Republicans than Democrats. I discuss what these new measures contribute in regard to theories of social group identity and our understanding of party identification in the U.S.