When can we realistically expect ordinary people to check the authoritarian ambitions of elected politicians? An answer to this question is key to understanding the most prominent development in the dynamic of democratic survival since the end of the Cold War: the subversion of democracy by elected incumbents and its emergence as the most common form of democratic breakdown. This article proposes an explanation according to which political polarization undermines the public's ability to serve as a democratic check: In polarized electorates, voters are willing to trade off democratic principles for partisan interests. The article presents evidence that supports this claim; raises questions about the real-world relevance of conventional measures of support for democracy; and highlights the importance of understanding the role that ordinary people play in democratic backsliding.