In the last decade, post-communist authoritarian regimes in Serbia, Georgia and Ukraine collapsed dramatically amidst popular upheaval. Hundreds of thousands protesters took to the streets of Belgrade, Tbilisi and Kiev to defy authoritarian rulers and their security forces, and to bring democratic opposition to power. The events attracted considerable media interest, revived hopes in the prospects of democratisation in the regions in which earlier transition from authoritarianism had not resulted in democracy, and also provided important lessons for democratic forces engaged in the struggle against authoritarian rule. And yet, post- communist democratic revolutions were only the most highly visible and apparent expression of the long-standing struggle of democratic forces against authoritarian regimes, which often spilled over from political institutions to the streets of their capitals and regional centres. Scores of popular protests and protest campaigns failed to dislodge Miloševid, Shevardnadze and Kutchma from power, but repeatedly undermined their rule, strongly shaped the identities, interests and capacities of both authoritarian regimes and opposition forces, as well as their evolving interaction, and thus ultimately contributed to regime change. This article explores a complex relationship between mass mobilization and the new species of authoritarianism, which mixes democratic procedures and authoritarian rule. Recent research has provided useful insights into the rise, development and consequences of competitive authoritarian regimes, and into the ways they end. However, these scholars pay little attention to the links between the new authoritarianism and protest politics, namely to the ways in which this regime type shapes mass mobilization, to the dynamics of protest politics and its interaction with regime actors, and its consequences for regime survival and change. I argue that competitive authoritarianism is inherently unstable and is especially vulnerable to mass mobilization. While the literature on competitive authoritarianism does not consider the exercise of power as a defining feature of regime types (Snyder 2006), I show that those competitive authoritarian regimes with neo-patrimonial features are especially exposed in this respect. I bring together insights from comparative regime analysis and research on social movements and contentious politics to show how the political context shapes mobilization and the dynamics of political conflict, and how this conflict may produce major political change.