This project uses archival records of the whip counts conducted by party leaders in the U.S. House to address significant scholarly disputes about the role of partisan institutions in Congress. A whip count is a private poll conducted by party leaders in which the positions of individual legislators are categorized as .yes,. .leaning yes,. .undecided,. .leaning no,. .no,. or nonresponsive. Detailed records of the whip counts conducted by House Democrats for 1955-1986 and House Republicans for 1975-80 have been compiled from the personal papers of former party leaders. Included are records for over 600 whip counts, covering hundreds of the most significant measures considered by Congress since World War II (e.g., federal aid to education in the 1950s and 1960s, the Vietnam conflict, the energy battles of the 1970s, and Reaganomics and U.S. involvement in Nicaragua during the 1980s). The research team will transform the archival materials into usable quantitative data, integrate relevant contextual evidence, and conduct the additional archival research necessary to incorporate more recent materials for the House and evidence from the Senate. Among other topics, these data will be used to evaluate the independent impact of party leaders in the legislative process. According to party-based theories of Congress, when policy preferences within the House majority party are homogeneous and preferences between the two parties are polarized, the majority party may be able to secure noncentrist outcomes that better reflect majority party viewpoints than chamber opinion as a whole. Other scholars, however, maintain that legislative outcomes derive from the preferences of rank-and-file lawmakers, rather than the machinations of party leaders. Attempts to resolve this dispute empirically have been undermined by problems of observational equivalence because scholars generally lack measures of member positions prior to the roll call decision. The records of past whip counts, however, can provide such a window into the evolving preferences of legislators in the days and weeks before floor action on major issues. In addition to the conceptual debate over party power, this study will address other important questions about the coalition-building process: What factors shape the size and contents of party legislative agendas in Congress? What is the distribution of preferences confronting the leadership prior to significant roll calls? What factors determine whether individual lawmakers will stay loyal or defect from the party line? How successful are party leaders at mobilizing support for party programs? And how do the answers to these questions vary by issue, party, and period? Broader Impact. The data sets created for this project will be made available to scholars and students via an elaborate website, providing the entire research community with valuable evidence about the dynamics of coalition building on Capitol Hill. Scholars and students alike will be able to conduct guided searches of the data base and download personalized data sets organized by bill, policy area, date, and legislator. Identifiers will be included to facilitate the merging of files with information from other on-line sources, such as the Policy Agendas Project at the University of Washington. The whip evidence will help scholars answer a range of questions, as well as inform student research for course assignments about the Congress. Additional data from congressional and presidential archives will be added as it becomes available. A long-term goal of this project, then, is to develop and maintain one of the more valuable and highly-used research websites about the American legislative process.