What drives Islamists’ democratic commitments? Does modernization turn them into committed democrats? Or do institutions rein in their authoritarian tendencies through political socialization and democratic habituation? This chapter critically reviews three theories that define the scholarly debate surrounding these questions while providing a historical and political context to all three cases. It first explores the history of modernization in Turkey, Egypt, and Tunisia and discusses the role of socioeconomic factors on the democratization of Islamist parties. Then it discusses the impact of institutions on party behavior and ideology, specifically the inclusion–moderation thesis to test its claims against the evidence we now have with the rise of Islamist parties to power. This survey reveals the limits of the institutional and ideational effects of inclusion. The final section turns to the strategic calculations of Islamist actors to discuss the role played by external factors, including regional and international developments. The central claim of the chapter is that existing accounts offer only a partial explanation failing to address diversity of perspectives and internal conflicts within Islamist parties.