Since 2011, the Arab world has seen a number of autocrats, including leaders from Tunisia, Egypt, Libya, and Yemen, fall from power. Yet, in the wake of these political upheavals, only one state, Tunisia, transitioned successfully from authoritarianism to democracy. Opposition parties forged a durable and long-term alliance there, which supported democratization. Similar pacts failed in Morocco and Mauritania, however. In Why Alliances Fail, Buehler explores the circumstances under which stable, enduring alliances are built to contest authoritarian regimes, marshaling evidence from coalitions between North Africa's Islamists and leftists. Buehler draws on nearly two years of Arabic fieldwork interviews, original statistics, and archival research, including interviews with the first Islamist prime minister in Moroccan history, Abdelilah Benkirane. Introducing a theory of alliance durability, Buehler explains how the nature of an opposition party's social base shapes the robustness of alliances it builds with other parties. He also examines the social origins of authoritarian regimes, concluding that those regimes that successfully harnessed the social forces of rural isolation and clientelism were most effective at resisting the pressure for democracy that opposition parties exerted. With fresh insight and compelling arguments, Why Alliances Fail carries vital implications for understanding the mechanisms driving authoritarian persistence in the Arab world and beyond.