The role of the U.S. House Rules Committee is consequential for theories of congressional parties, yet its role during the "conservative coalition" era is not well understood. We systematically analyzed the politics surrounding all special rules considered in Democratic Congresses from 1937 to 1952. We found that Rules repeatedly used its agenda power to push to the floor conservative initiatives that were opposed by the Democratic administration, the Rules Committee chair, and most northern Democrats, especially in Congresses that followed Republican election gains. The 44 conservative initiatives we identified include many of the most important policy issues considered during the period. Our findings challenge the idea that the majority party has consistently enjoyed a veto over which initiatives reach the floor, and they underscore the limits of roll-call-vote analysis in assessments of agenda control.