How do citizens in the Arab world hold their governments to account between elections? Diagonal accountability mechanisms in the literature show how citizens can constrain executive power by imposing reputational costs, by using legal action, or through watchdog oversight. However, citizen mobilizations in the Arab world are often autonomous, reflecting low political trust and ineffective political parties and therefore weakening potential accountability mechanisms. This article uses a structured, focused comparison of protest episodes during the Tunisian transition to theorize three alternative mechanisms used in autonomous mobilizations. Autonomous movements develop legitimacy for their claims by reinterpreting initial grievances as legitimate claims for greater popular participation in decision-making. Although these movements all insist on their independence from parties and unions, they develop temporary and expedient alliances with political actors for greater leverage. When movements have sufficient local resources, they try to establish lasting collective capacities to demonstrate alternative models of development. These findings contribute to a richer understanding of the varied mechanisms behind accountability processes in new democracies by showing how autonomous movements deploy alternative strategies to shape the quality of their emerging democratic system.