DescriptionThe United States has experienced a wave of political protest action since the 2016 U.S. Presidential Election. The present study investigated possible psychological motivators for this protest action by liberals and moderates. The potential motivators included perceived moral violations by the president, protesters’ social identity (defined as political ideology), opposition to the president’s political policies, perceiving the president as having many character failings, and dislike of the president. The study employed a survey measuring political protest activity, as well as measures capturing all the hypothesized predictors. Data was collected from two samples, university undergraduates and Mechanical Turk workers, and analyzed together as one combined sample. Results revealed that protest behavior since the election was predicted by perceived individualizing moral violations by President Trump, and included an interaction between individualizing moral violations and individualizing moral foundations, such that protest was highest when both violations and foundations were also high. In addition, protest behavior was predicted by perceived binding moral violations by President Trump, and by perceived economic/government liberty moral violations by President Trump. Further, protesters’ social identity (political ideology), and opposition to President Trump’s policies also predicted protest behavior. Finally, protest was also predicted by perceived character failings of President Trump, and by dislike of President Trump. Altogether, these results suggest that protest activism is predicted by dissatisfaction with the president in moral and policy realms, as well as a general dislike of him and concerns about his character. It is possible that protest activism is triggered when people encounter a vast array of aversive actions and qualities (real or perceived) in their current leader. In addition, although this study was restricted to protesters who were liberals and moderates, it is possible that these findings would generalize to protesters of any political ideology.