The recent rise in using cloture—a Senate procedure to limit debate and force a vote—to begin debate on legislation is not simply the product of growing partisan obstruction; it also reflects a breakdown in the Senate’s amendment process. As opportunities to offer amendments declined, minority-party senators became less willing to cooperate in bringing bills to the floor. This link between cloture on the motion to proceed and fewer amendment opportunities once debate began was made explicit in a gentleman’s agreement between Majority Leader Harry Reid, D-Nev., and Minority Leader Mitch McConnell, R-Ky., at the start of the 112th and 113th Congresses. McConnell assured Democrats that Republicans would not routinely filibuster (i.e., block by extended debate) such motions, and Reid pledged not to routinely fill the amendment tree—meaning occupying all available amendment slots to prevent others from offering amendments—once the Senate got on a bill. The Reid-McConnell agreement thus illustrates that obstruction before debate and exclusion during debate are linked.
But the Reid-McConnell agreement did not last because the underlying incentives remained unchanged. Democratic and Republican majorities alike have continued to file cloture on motions to proceed to bring bills to the floor. And they continue to fill the amendment tree to block amendments as soon as debate begins. This dynamic creates a self-reinforcing cycle. Minority-party senators have little reason to help the Senate get on a bill if doing so does not result in a genuine opportunity to offer amendments. And Senate majorities have little choice but to rely on cloture when unanimous consent to begin floor debate becomes harder to secure. In that sense, procedural obstruction on the motion to proceed is, at least in part, a response to procedural exclusion in the amendment process. If invoking cloture on the motion to proceed simply produces a filled amendment tree and a closed floor, the minority has little incentive to cooperate.
