The Senate today is an institution in decline. It is paralyzed – unable to legislate, much less deliberate.

The Senate’s plight is reflected in the near-total deterioration of its amendment process.

For example, senators offered a paltry 147 floor amendments between January and September of this year. Compare that to the 568 amendments they offered during the same period in 2015 and the 668 in 2009. At the present rate, Senate amendment activity could increase by as much as 250 percent over the next 15 months and still fall short of the level observed in the first nine months of 2015 alone.

This is the culmination of a broader trend going back three decades. During that time, Senate majorities have increasingly empowered the institution’s majority leader to prevent senators from offering amendments to achieve their legislative priorities.

The majority leader blocks senators from offering alternative proposals by filling the amendment tree, i.e., offering the maximum allowable number of amendments to legislation before other senators have had a chance to debate the measure and offer their own amendments.

Once used sparingly in extraordinary circumstances, the tactic is now routine and well-documented. But less appreciated is the extent to which its normalization in recent years represents a radical break from the Senate’s past practice. Also, less understood is how precisely the tactic empowers the majority to pass its agenda, given that the minority can still filibuster the underlying legislation.

Recent research suggests that the amendment process gradually evolved to facilitate the orderly consideration of the Senate’s business. The direction in which it evolved was informed by the Senate’s effort to balance the need for order in its work with the imperative of legislative deliberation.

While the Senate’s first amendment trees only permitted two amendments to be pending at the same time, they were expanded in response to member demands by adding new branches. The result was to increase the number of amendments that could be pending before the Senate simultaneously.

Notwithstanding this increase, members maintained order by adhering to the principles of precedence first compiled for the Senate in Thomas Jefferson’s A Manual of Parliamentary Practice for the Use of the Senate and still followed today. In general, those principles held that senators should have an opportunity to amend legislative text proposed to be stricken and/or inserted before the actual vote to strike and/or insert said text.

Analyzing how the Senate’s current amendment trees came to be underscores the extent to which using them to block amendments is a perversion of the Senate’s rules and practices. That is, the precedents underpinning the trees are now being used for a purpose fundamentally at odds with the one for which they were first created. Instead of facilitating the orderly consideration of amendments on the Senate floor, they are now being used to block the consideration of amendments altogether.

This suggests that the act of offering amendments no longer serves as a way in which the Senate can arrive at a greater understanding of what its members think about a given issue. Instead, the amendment process is commonly viewed as the last hurdle needed to be surmounted before a preferred bill can be sent to the House or to the president’s desk to be signed into law. To the extent that controversial amendments are permitted on legislation, frequently their consideration is structured in such a way as to guarantee their defeat. This requires channeling all decisions regarding which amendments can be offered to legislation through a single veto point (i.e., the party leaders or bill managers). Once established, such a veto point enables the leadership and/or bill managers to exercise disproportionate control over which amendments will be made pending to legislation on the Senate floor and to set the terms according to which those amendments will be disposed of.

Establishing a veto point is accomplished by putting the Senate in a parliamentary situation in which unanimous consent is needed to get an amendment pending under one of the four amendment trees. The primary tool utilized by the majority leader to accomplish this is the tactic of filling the amendment tree (or offering a blocker amendment in one of the available slots such that further amendments are precluded by the principles of precedence if that blocker amendment is pending). No amendments are in order once all the extant branches on the tree are occupied. At that point, the majority leader and/or bill manager is free to focus on negotiations with interested rank-and-file colleagues to reach a unanimous consent agreement that provides for several amendments and a vote on final passage without having to worry about a senator jeopardizing the legislation’s prospects by offering a controversial or otherwise unwanted amendment without permission.


As noted, the majority leader (or bill manager) may also offer a “blocker” amendment to establish the veto point. For example, an amendment offered to branch C in the chart above would serve as a blocker amendment if offered first and in the form of a motion to insert (or strike and insert). Once pending, any other amendment offered directly to the amendment in the nature of a substitute (ANS) would require consent to get pending (which would presumably be denied if the majority leader/bill manager wanted to block the amendment).

This tactic is less aggressive than completely filling the amendment tree, in that it typically leaves a few branches open for possible amendment. However, these branches are rarely connected to the ANS directly. For example, in the hypothetical example, the blocker amendment leaves branches E and F (on the left side of the amendment tree) open. Branch D (second degree to C on the right side) is also left open. These branches do not present the same challenges to proponents of the bill because their impact would be minimal if the amendments pending there prevailed. The majority leader could move to table C to prevent a vote on D on the right side of the tree. Additionally, adoption of E and F on the left side of the tree would be negated once the Senate adopts the ANS.

Once the Senate is in a parliamentary situation in which unanimous consent is needed to get an amendment pending to legislation on the floor, the majority leader can use his increased leverage to secure a higher vote threshold for adoption of an amendment. The majority’s desire to limit the minority’s ability to attach what it considers poison-pill amendments to legislation it supports is thus reflected in the dramatic increase in the use of unanimous consent agreements to set 60-vote thresholds for adopting amendments.  The majority leader uses the threat of not allowing amendments to get pending to compel individual senators to agree to the higher vote threshold on their amendment, even though doing so means that the amendment will most likely be rejected.

The routine practice of filling the amendment tree in the Senate today, coupled with the cloture process to end debate, effectively prevents members from being able to perfect legislation before it receives an up-or-down vote on final passage. Instead of a deliberative process designed to discern the true sense of the institution’s membership on an issue, senators are confronted with a fait accompli. This practice is inconsistent with the longstanding rules and practices on which the amendment process is based.

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