Party Polarization in the U.S. Congress.

The growing divide between Republicans and Democrats in Congress is well documented, but its causes are not well understood. This article finds that almost the entire growth in party polarization in both chambers since the early 1970s can be accounted for by the increased frequency of and polarization on procedural votes. In comparison, final passage votes are relatively less frequent and not nearly as polarizing. Only when changes in the electorate interact with the legislative process can party polarization be properly understood and analyzed. This article also finds that the constituents' voices have become barely audible on procedural votes. These findings have important consequences in how procedural and final passage roll calls are voted on in Congress, viewed by the electorate, and interpreted by political scientists. This article argues that procedural voting needs to be taken more seriously by congressional observers and analyzed more carefully by political scientists if members are expected to view procedural votes as something more than "mere procedure." ..PAT.-Unpublished Manuscript [ABSTRACT FROM AUTHOR]