Since 9/11, evangelical Christians have contributed to drawing boundaries of inclusion and exclusion in the American democratic public sphere, with attention to Muslims as ostensible religious, political, and racial outsiders. This project analyzes evangelical struggles over the authority to define Islam and Muslims through a mixed-methods analysis of 200 evangelical books on Islam and three comparative case studies. It investigates the competition among evangelical leaders for authoritative “ethnographic capital” to prescribe orthodox understandings of Islam. Through this analysis, the project explores the role of evangelical leaders and institutions in shaping the boundaries of democratic participation in the American public sphere.