Moderate Caucuses in a Polarised US Congress

Despite putting themselves in a thorny relationship with heavy-handed party leaders, some US legislators continue to join moderate coalitions. To understand why, this article derives seven explicit hypotheses concerning electoral, institutional, and strategic dimensions and tests them on two moderate coalitions from the 107th to the 110th Congress (2001–8): the Republican Main Street Partnership and the New Democrat Coalition, along with the Senate's ‘Gang of 14’ during the 109th Congress (2005–6). The article finds that, as expected, a member's ideology and previous affiliation strongly predict who joins these caucuses. What is surprising from the findings is that the constituencies' partisanship does not always predict the legislators' decision to be a moderate caucus member. There is little evidence that more electorally vulnerable members join these caucuses; on the contrary, when it does matter, members from competitive districts appear to stay away from moderate coalitions. Therefore, the findings call into question the prevailing ‘constituency-based’ understanding of moderate coalition membership in a polarised Congress and call for a new examination of electoral connection between moderate members and moderate caucuses.