Much attention has been given to recent (real or perceived) erosion of democratic norms and practices in countries such as the United States, Brazil, Hungary, Poland, and the UK. Some have lamented that much of this democratic backsliding has been engineered by charismatic leaders unchecked by their parties---as the traditional bulwarks of liberal democracy. In this paper, we formally model the interaction between a leader occupying the chief executive and his party. We show that when parties are highly reliant on a leader's charisma to win elections, they grow less able to sanction their behavior in office. This is particularly true in settings characterized by high levels of ideological polarization. This inversion of the power dynamic between parties and politicians increases the likelihood that demagogic politicians are able to enact anti-democratic policies. We seek to test these theoretical predictons using cross-national data on leaders characteristics, changes in the quality of democracy, and autocratic reversions.