This article explains coup activity in democracies by adapting insights from the literature on commitment problems and framing coup around the threats leaders and potential coup plotters pose to each other. I claim democratic constraints on executive power inhibit a leader’s ability to repress threats from political rivals. Though this decreases motivations for coup attempts, it also makes democracies more vulnerable should a coup attempt occur. Consequently, democratic constraints on executive power do not reduce the frequency of coup attempts, but coups attempted against democracies are much more likely to succeed. Using several data sets of coup activity and democratic constraints, I find significant differences in coup activity in democracies and non-democracies. Relative to civilian non-democracies, democracies are about half as likely to use coup-related repression, but they face a similar frequency of coup attempts. Plots against democracies are nearly twice as likely to succeed.