The Arab Spring startled all Arab autocrats but toppled few of them. We find there were no structural preconditions for popular uprisings, but two variables conditioned whether domestic opposition would succeed. First, oil wealth gave rulers the resources to preempt or repress dissent. Second, a precedent of hereditary succession signaled the loyalty of the coercive apparatus to the ruler. Consequently, mass revolts deposed incumbents in only the three non-oil rich, non-hereditary regimes of Tunisia, Egypt, and Yemen. Where oil rents or hereditary rule prevailed, regimes violently suppressed peaceful protests (Bahrain, Syria) and only lost power through foreign-imposed regime change (Libya).