Dimensionality in Congressional Voting: The Role of Issues and Agendas

Abstract

Congressional preferences are frequently categorized by a liberal to conservative dimension that splits the two-party system in the modern period. However, recent studies of voting in Congress have challenged that conception (Roberts et al. 2007, Crespin and Rohde 2010, Dougherty et al. 2010). Scholarship that relies exclusively on the roll call record to explain congressional preferences may not account for other dimensions that exist in the legislative process. Partisan agenda control may further lower the dimensionality suggested by roll call voting. In this paper, the strength of the unidimensional model is tested. First, issue areas that should theoretically be poorly accounted for by the unidimensional model are examined. These issues are based on Aage Clausen's "law of categorization" which argues that members of Congress have consistent issue preferences that vary based on the policy considered (Clausen 1974). Policy areas that vary by region are examined, as the economic benefit of a constituency (Fenno 1978) or the political culture of a district should affect voting preferences in Congress (Elazar 1994). The results of this analysis suggest that the unidimensional model performs poorly on many of these issue areas. Second, this paper demonstrates how the changing nature of the congressional agenda affects the importance of extra-dimensional preferences. By creating models using a subset of each Congress, this study shows that issues like abortion have risen on the agenda while a civil rights issue dimension is no longer active. Finally, using the evidence gathered in the previous sections, this paper examines the importance of issue areas on procedural votes as compared with roll calls which change the ideological content of a bill. The results suggest that parties during the Clinton years have overcome these issue dimensions during procedural votes, but votes that affect policy legislators may revert to issue based preferences. Overall, the results of this paper suggest that within specific issue areas, meetings of Congress, and types of roll calls, there is a systematic under-performance of the unidimensional model of preferences.