Individuals self-categorize within an international context, and this supranational identity shapes expectations for their own political system. Those individuals in post-Communist countries who believe that their country's primary international orientation should be towards the European Union have a more participatory view of politics and are more politically active. This study develops a social identity explanation of political behavior, and tests the explanation utilizing maximum likelihood and non-parametric matching methods in a 2004 survey of political attitudes in Moldova. Moldova's patchwork of identities, mixed historical legacy, and salience of supranational association make it an excellent case for study. The analysis finds strong support for the effect of supranational identity across a wide range of attitudes and activities.