Most studies of policy feedback have focused on processes of self-reinforcement through which programs bolster their own bases of political support and endure or expand over time. This article develops a theoretical framework for identifying feedback mechanisms through which policies can become self-undermining over time, increasing the likelihood of a major change in policy orientation. We conceptualize and illustrate three types of self-undermining feedback mechanisms that we expect to operate in democratic politics: the emergence of unanticipated losses for mobilized social interests, interactions between strategic elites and loss-averse voters, and expansions of the menu of policy alternatives. We also advance hypotheses about the conditions under which each mechanism is likeliest to unfold. In illuminating endogenous sources of policy change, the analysis builds on efforts by both historically oriented and rationalist scholars to understand how institutions change and seeks to expand political scientists’ theoretical toolkit for explaining policy development over time.