Much of the literature on partisan agenda setting in Congress focuses on the majority’s ability to exercise negative agenda control. As a result, the empirical emphasis has been on "rolls," or how often the majority of the majority party opposes legislation that nonetheless passes. Although interesting, rolls are only one source of majority party failure. The other source, largely unexplored in the literature, is when the majority of the majority party supports legislation that is subsequently defeated. These cases represent "disappointments," and are a means to determine how effective the majority party is at exercising positive agenda control. Making some basic modifications to a standard spatial model of agenda setting, we articulate why and where we might expect the majority party to fail to exercise positive agenda control effectively. We then derive hypotheses regarding (1) which members should vote "no" on roll calls that result in a disappointment and (2) why disappointments vary on a Congress-by-Congress basis across time, and test them using a dataset of final-passage votes on House bills in the post-Reconstruction era.