Bipartisan Coalitions More Likely as Congress Becomes More Polarized, Dartmouth-Miami University Study Finds


April 6, 2017 – Congress passed a surprising number of bills between 1981 and 2008 with bipartisan majorities large enough to withstand a presidential veto despite growing ideological divisions between Democratic and Republican lawmakers. A new Dartmouth - Miami University study demonstrates that legislative leaders used their increased control over procedures, a development that coincided with greater polarization, to create veto-proof bills. Presidents, in turn, gleaned useful information from such lopsided tallies to deploy their veto power strategically. The findings are published in Political Research Quarterly in an OnlineFirst manuscript ahead of the June print issue. (A pdf of the study is available upon request).

 “Members of Congress often seek veto-proof bills to protect constituency benefits or provide political cover on tough votes. As party leaders gained leverage over the legislative agenda in the wake of increased polarization, oversized coalitions became more likely,” says Dartmouth Professor of Government and Frank J. Reagan Chair in Policy Studies, Emerita, Linda Fowler, co-author of the study.

 Most research on Congress focuses on how the majority party uses procedures to prevent minority obstruction. This study breaks new ground by examining the efficacy of legislative maneuvers in generating super-sized coalitions and by showing how the final vote tally signals the president about the costs of a veto. The study relies on a unique data set of over 3,400 bills to examine procedures that have received less attention from scholars, particularly combining multiple bills into a single package, and it develops new means for identifying politically salient bills based on a bill’s policy content and its page length.

 The authors report positive statistical effects for procedural maneuvers on the probability of bills with a super-majority, which they define as an outcome with a recorded vote of 66 percent in one or both chambers. They also find that the watershed election of 1994, which was instrumental in promoting greater party influence on members’ decisions, increased the likelihood of veto-proof outcomes. 

 Presidents have several options when a bill reaches the Oval Office: sign the measure without comment, add a rhetorical or constitutional signing statement to flag the bill’s positive or negative aspects, or reject it with a veto. Each of these options can influence public perceptions of the president and affect the executive’s future relationships with the legislative branch. Will presidents be blamed for legislative failure or appear weak if they accept a bill that they previously opposed? A bill’s legislative history and its final tally convey valuable cues about the likely congressional reaction and thus aid the president in evaluating the costs and benefits of signing, appending comments or rejecting a measure. From the Reagan years beginning in 1981 through 2008 with the George W. Bush administration, the authors find that presidents focused their veto power on bills that offered a chance for bargaining or on which they had issued veto threats.

 Citizens and pundits often assume that the White House dominates Congress but this study demonstrates that lawmakers can adapt their institution to circumvent the president’s most formidable tool—the veto—when their political interests are at stake.

Linda Fowler is available for comment at