Why did Tunisia alone peacefully transition from authoritarian rule in the wake of the Arab Spring? This question addresses the broader sociological puzzle of variation in revolutionary outcomes. Drawing from rich archival and interview data, I pursue a microanalysis of three pivotal moments in the Tunisian case. The dissertation reveals endogenous forms of causality that cast doubt on the explanatory value of dominant structural accounts, which emphasize the decisional impact of positional interests, dispositions and an objective balance of power. In contrast, situational logic trumps motivational or contextual factors inherited from the long run, because actors facing the confusion and instability characteristic of revolutionary and post-revolutionary situations make their behavior conditional on one another. Hence the aggregate outcome of revolutions is sensitive to small events, and thus probably unpredictable. But we can explain individual and collective behavior by develop- ing systematic propositions about the processes by which actors understand their situation and adjust to one another in these exceptional conditions. The first chapter investigates what drives the stance of armed forces facing an uprising. Soldiers and policemen make or break revolutions. Yet we know little about why they betray a dictator or stay loyal in the face of mass protests. I investigate the dynamics of the mutiny that overthrew Zine el-Abidine Ben Ali on 14 January 2011, turning the Tunisian uprising into a regional wave of unrest. I trace the likelihood of rebellion to the moment when reserve forces face the imminent prospect of using large-scale lethal violence against civilians. The moment represents a critical decision, manifested in collective doubt and uncertainty. This makes professional armed forces susceptible to cascades, which are driven by expectations rather than preferences, positional interests or institutional rules. Hence the stance of the institution as a whole is highly sensitive to small events that shape officers’ beliefs regarding their colleagues’ likely behavior. The mutiny of a handful of officers can tilt the institution as a whole. Flows of information prove to be decisive. Hence accounting for the variation in outcomes of mass uprisings requires shifting the explanatory focus toward endogenous, locally proximate causes. The argument has implications for the study of revolutions, authoritarian breakdown, civil-military relations, and nonviolence. The second chapter draws from a study of the prelude to Tunisia’s 2011 “roadmap” to investigate the emergence of political pacts after the revolutionary collapse of a personalist regime. Such pacts feature prominently in dominant accounts of transitions from authoritarian rule, but how they come about is poorly understood. I argue that prevailing strategic evaluation hypotheses illuminate negotiators’ motivations, but fail to theorize how actors form a convergent view of their respective strengths, which is necessary to avoid conflict. In post-breakdown moments, public events, particularly mobilization events, provide the primary yardstick actors use to evaluate the balance of power. Well-attended street mobilization creates common knowledge about the capacity of the group and can focalize its stance, which allows it to overcome collective action problems, strengthens its bargaining position, and provides cues to the solution of the bargaining problem. A mobilization contest unambiguously favoring one side encourages the weaker side to concede, facilitating agreement. The argument has important implications for bargaining, collective action, and political transitions. The third chapter analyses the Tunisian political crises of 2013 to explain group formation and contentious mobilization in reaction to violence. Processes of contentious escalation engage the definition of what constitutes the relevant actors: individuals mobilizing together broaden their relevant frame for action to a group with whom they identify. This point problematizes general accounts of mobilization that take groups for granted and anchors a line of inquiry focused on shifts in group boundaries as a prelude to action. I argue that public, symbolic acts of violence reinforce group boundaries associated with the act’s symbolism while weakening those made irrelevant because the violent act communicates the perpetrator’s intent to target a group and generates negative emotions among those who identify with the victims. Anger reinforces relevant cleavages, diminishes tolerance for ambiguity – fostering a logic of “with us or against us” – and provides a motivational basis for mobilization as a defensive display of solidarity. When well-attended, mobilization fosters a sense of confidence and a perception of opportunity among contenders, facilitating further action. The argument locates the emergence of coalitions of contention in the coevolution of patterns of symbolic events, interpretation and action. In doing so it theorizes the effects of public violence, mediated by anger. It has broad implications for the study of social movements, community conflict, polarization, and descent into civil war.