This article outlines and tests a novel theory of how national identities affect political attitudes and policy preferences. Comparative National Self Theory (or CNST for short) brings together two separate lines of research, which have perpetuated a disciplinary and methodological division. The first line, rooted in social and political psychology and relying on quantitative methods, focuses on the nation’s position in a symbolic field: studies ask how beliefs about national boundaries and hierarchy between nations affect people’s views on issues such as immigration policy and foreign affairs. The second research line, rooted in the humanities and cultural sociology and relying on hermeneutic methods, focuses on national meaning-making: it links political attitudes to collective memories, myths, and symbols that make “thick” national identities and examines how leaders selectively employ parts of a national cultural toolbox to mobilize public support. CNST merges the two parallel research lines by suggesting that when people process information about significant national policies, they apply a dual-comparison framework (cues from public speakers and the media encourage people to apply it): “us versus them” comparisons of the nation’s symbolic value relative to other groups, and “current us versus idealized us” comparisons of the nation’s current state and actions to an idealized image of the nation based on national narratives. CNST entails two additional steps: It elaborates on the affective mechanisms that mediate the impact of meaning-making via the dual-comparison framework on attitude formation. CNST then specifies the crucial role of people’s core nationalistic beliefs, which moderate the processing of messages and cues about national policies via the dual-comparison framework. The article presents the findings of a study that tested CNST through a survey experiment of attitudes about undocumented immigrants in Israel.