Political protests increasingly play a critical role in shaping politics in democracies. What political consequences did the growing global protest cycle bring about within democratic countries with unrest? Drawing on social identity theory, I argue that protest events, which targeted specific parties or leaders, would serve as a focal event that enhances voters’ attachment to partisan identity. Targeted protests provide open information containing a specific political message about targeted candidates or parties to the public. Accordingly, exposure to protests may activate and reinforce pre-existing partisan identities and ultimately trigger affective polarization at the mass level. To examine this argument, I use cross-national survey data to test whether protests targeting ruling parties increased the level of mass polarization among 38 democracies between 1996 and 2021. The findings have implications for understanding the impact of protests on voting behavior and the process of polarization in democracies.