Robert C. Byrd, America’s longest serving Senator, was fond of noting that the two great rights of Senators are the right to debate and the right to amend.  Not generally governed by germaneness requirements, the Senate amendment process has historically been open and robust.

Non-germane amendments have been an important way for the minority party to bring issues to the floor for disposition.  When amendments have been restricted, it has customarily been by unanimous consent or by exercising self-restraint.

In recent years, the Senate amendment process has become much less open.  Using a device called “filling the amendment tree,” the Majority Leader has substantially curtailed the chance to shape legislation through amendments.  Although such terms and methods are ill-understood outside the Senate, they are easy to explain.

To create procedural orderliness, the Senate limits the number of amendments that can be pending at a single time.  An amendment tree expresses these limits in diagram form.  Under longstanding Senate practice, the Majority Leader has preferential recognition over other Senators.  Majority Leader Harry Reid has used this power to propose amendments that fill all available branches on the amendment tree.  When he does that, other Senators are stopped from offering amendments of their own, unless the Leader agrees to set one of his amendments aside to make room.  Often, a filled tree is used to bar amendments completely.

Leader Reid did not invent this practice.  To varying degrees, it has been used by Leaders since the middle 1980s.  But the use of filled trees has sharply accelerated.  Leader Reid has executed this strategy over 85 times, over twice as often as all predecessor Leaders combined.

Frustration among minority Senators is high.  Some have unsuccessfully used tabling motions to knock Reid amendments off the tree and create amendment opportunities for themselves.  Tabling requires a simple majority vote, which the minority has yet to muster for this purpose.  Other Senators have attempted extraordinary procedures that would have the effect of expanding the tree.  These also take a majority and have failed.

Defenders of the Leader’s approach contend it keeps the body focused on pending legislation and prevents the Senate from being bogged down with irrelevant and politically-charged amendments.  Critics say that by impeding Senators’ ability to amend legislation, filled trees impair representative government.  One thing is beyond argument: the tactic is both a response to and a driver of a breakdown in comity and entrenchment of Senate dysfunctionality.