Senators still love the legislative filibuster

Last week, 61 senators reaffirmed their commitment to allowing filibusters against legislation. Senate Republicans’ use of the nuclear option to thwart Democrats’ filibuster against Supreme Court nominee Neil Gorsuch led many senators and observers to predict the end of the filibuster. Not so fast.

There are three compelling reasons most senators find it in their interest to preserve legislative filibusters.

First, filibustering empowers senators as individuals, so each senator can draw attention to the issues he or she cares about the most.

Second, filibustering provides the minority party with a defense against majority party attempts to limit floor debate. Without it, senators fear, major bills would zip through the chamber without discussion or amendments, as they do in the House of Representatives.

Third, and perhaps most important, the filibuster provides political cover for cross-pressured Republicans. As I explained two months ago:

Filibusters help members of the majority party when they are pressured to support proposals that they privately believe are bad policy or risky politics. That is, there are members of the majority party who privately believe their party’s proposals are politically dangerous or terrible policy, but they are afraid to publicly defy their party leadership. In a simple-majority legislature, these conflicted members would have to make difficult choices between their private views or personal interest and the position of their party, backed by a populist president or powerful interest groups. In a supermajority legislature, on the other hand, conflicted legislators can publicly support their party’s position while privately applauding the obstruction of the minority party.

Consistent with this logic, the Republican senator who took the lead in reaffirming the legislative filibuster last week was Susan Collins of blue-state Maine. She and Chris Coons (D-DE) amassed 61 signatures (32 Dems, 29 GOP) on a letter to the majority and minority party leaders of the Senate.

Collins’s website provides the full list of signatories to the letter. I compared the signers to non-signers based on two possible explanations: a) years of Senate experience, and b) Trump support in the 2016 election (specifically Trump’s percentage of all votes for Trump and Hillary Clinton). The first variable tests the notion that senators come to appreciate filibustering over time, while the second tests for greater support for filibustering among moderates.

Let’s look at Democrats first. Here are the Democrats who signed the Collins-Coons letter (dark blue triangles) and those who did not sign (light blue circles).

Just scanning the figure, it looks like Democrats in Trump states may be more likely to want the filibuster to continue. These senators gain the most from continuing a system in which they are pivotal, so that Republicans seek them out to bargain for their votes on cloture.

Next, let’s look at Republicans, with signers in red triangles and non-signers in orange circles. Here it looks like there may be a slight bias toward more senior Republicans and those representing swing states.

And yet a simple multivariate statistical test* of these patterns finds no clear relationship between state partisanship, seniority, and support for the legislative filibuster. Nor did party affiliation, so Democrats were not more likely to sign the letter than Republicans. Nor did FiveThirtyEight’s “Trump scores” of roll call voting correlate.

Put simply, the signatories seem to represent a cross section of the Senate. The desire to maintain the legislative filibuster does not seem to be confined to a small faction, or Democrats plus moderate Republicans, or Senate veterans. Instead, a broad set of senators prefer to continue making decisions together. This commitment will be critical as the Senate returns from spring break and takes up major legislation that is vulnerable to a filibuster, like funding for the rest of fiscal year 2017.

*Note: A probit analysis in STATA of all 100 senators with “signed letter” as the dependent variable and Trump’s two-party presidential vote as one predictor, seniority as a second. Variations included a model with [Democrat] as a binary predictor variable and models with a) Absolute deviation from 50% Trump vote, and b) adjusted FiveThirtyEight Trump score so Democrats’ score was [100-Trump score], making it a measure of party unity. All results were statistically insignificant at conventional levels.