This research tests whether American's evaluations of the president have become more volatile in the postwar era. If the American public has become more volatile, less consensual and more uncertain in their evaluations of the president, it becomes more difficult for presidents to build and maintain legislative coalitions, unify domestic actors behind foreign policy initiatives, and maintain their own electoral coalitions. The proposal has two parts. The first explores changes in aggregate, group and individual bases of presidential approval. This part develops new measures of volatility in assessing Presidential approval. The second part turns toward the consequences of volatility for presidential success in Congress. This study uses new methodological techniques to combine public opinion poll data and legislative roll calls. These data constitute a new and valuable resource for scholars of the Presidency and Congress.