Copyright © 2015 by Annual Reviews. All rights reserved. In many democratic polities, constitutional courts significantly shape the political landscape. Yet, how they are able to do so is a puzzle: With limited resources at their disposal, and no direct powers of enforcement, judges must rely on the willingness of executives and legislators to comply with their decisions and to respect judicial authority. This essay surveys recent literature that has explored the conditions that sustain judicial authority. I contrast explanations that highlight the benefits that independent courts can provide to other policy makers ("endogenous explanations") with explanations that emphasize the constraints that keep executives and legislators from undermining the judiciary ("exogenous explanations"). I conclude by exploring the role of strategic judicial behavior in maintaining and expanding judicial power.