This article explores how interest groups decide policy positions through case studies of three organizations' shifting stances on the issue of immigration. In all three cases, the AFL-CIO, the Sierra Club, and the Christian Coalition, issue positions are signaling mechanisms central to the construction of an organizational identity. Leadership considers the message the stance on a policy issue sends to potential constituents and allies. Organizational agendas are one tool used by leaders to craft new narratives about what the group stands for, who the group represents, and who belongs. Key determinants of leaderships' calculation over redrawing the boundaries of inclusion and representation and what signal an issue stance will convey includes organizational strength and a reading of a shifting political terrain. An evolutionary metaphor, instead of a rational actor model, is better suited to understand this critical component of interest group behavior, agenda setting.