The first Islamist parties to come to power through democratic means in the Muslim world were those in Turkey, Tunisia, and Egypt. The Justice and Development Party (AKP) won the 2002 election in Turkey, and Ennahda (Renaissance Party) in Tunisia and the Muslim Brotherhood in Egypt were both elected in the wake of the Arab uprisings of 2010/11. Yet only Ennahda could be said to have fulfilled its democratic promise, with both the Turkish and Egyptian governments reverting to authoritarianism. Drawing upon extensive fieldwork in three countries, Sebnem Gumuscu explains why some Islamist governments adhered to democratic principles and others took an authoritarian turn following electoral success. Using accessible language, Gumuscu clearly introduces key theories and considers how intra-party affairs impacted each party’s commitment to democracy. Through a comparative lens, Gumuscu identifies broader trends in Islamist governments and explains the complex web of internal dynamics that led political parties either to advance or subvert democracy.