An Amendment Tree Guide

The amendment process members follow in today’s Senate has evolved over time. It is governed by the Senate’s Standing Rules (XV, XVI, and XXII) and, to a greater degree, its precedents (i.e. past parliamentary practice). Taken together, the Standing Rules and precedents specify the legislative procedures that determine when and under what conditions members may offer amendments to legislation (or other amendments) on the Senate floor.


Amendment Types

Amendments can be distinguished in three ways. 

First, amendments vary based on their instructions, or form. Amendments either insert language in an underlying measure, strike language from that measure, or strike and insert language. 

Second, and relatedly, amendments are categorized as either substitute or perfecting depending on the effect they would have on the text of the underlying measure. A substitute amendment strikes all of the text available and inserts alternative text in its place. All other amendments are considered perfecting amendments. Substitute amendments always strike and insert language. An amendment that strikes everything in a measure after its enacting (or resolving) clause and inserts new text is referred to as an amendment in the nature of a substitute (ANS). Perfecting amendments may strike text, insert new text, or strike existing text and insert new text.

Finally, amendments are distinguished based on degree. First-degree amendments are those offered directly to a measure pending on the Senate floor. Any amendment offered to a pending first-degree amendment is considered a second-degree amendment. Third-degree amendments are amendments offered to pending second-degree amendments. 

In the eighteenth and nineteenth centuries, senators generally considered competing first- and second-degree amendments to be third-degree amendments, and thus prohibited. Put differently, they defined as a “third-degree amendment” any amendment offered on the Senate floor after more than two amendments were already pending. For example, Henry Cabot Lodge, R-Mass., a former President pro tempore and Senate majority leader, stated on the Senate floor in 1914 that “the number of amendments pending is the test of the degree of the amendment.” 

Competing first- and second-degree amendments are permitted in certain circumstances today. But, as in 1914, the Senate still prohibits competing first- and second-degree amendments in various situations. When competing first- and second-degree amendments are still prohibited under the Senate’s existing precedents, I refer to them as horizontal third-degree amendments. I refer to literal third-degree amendments (i.e. an amendment to an amendment to an amendment) as vertical third-degree amendments.


Principles of Precedence

The Senate’s amendment process is governed by principles of precedence. These principles help members maintain order while facilitating deliberation on the Senate floor. They are derived from English parliamentary law and were first compiled by Thomas Jefferson in A Manual of Parliamentary Practice for the use of the Senate, written during his tenure as Vice President and President of the Senate (1797-1801). Today, these principles provide additional procedural guidance in situations for which the Senate’s rules do not provide explicit direction.

According to the Manual, committee amendments are considered on the Senate floor before floor amendments (i.e. those amendments proposed to a measure during committee consideration) (p. 44). Senators cannot amend legislative text more than once. Consequently, senators should have an opportunity to amend text proposed to be stricken and/or inserted before the actual vote to strike/insert said text (pp. 57, 61). Additionally, motions to commit have precedence over motions to amend (p. 54). And, as noted above, amendments may be amended in the second degree, but third-degree amendments are not in order (p. 56).


The Amendment Tree

The way in which the Senate applies these principles today makes possible four different amendment trees. An amendment tree is simply a way of depicting the maximum allowable number of amendments that may be pending to a measure at the same time. It is important to remember that the Senate’s current amendment trees are not static and have changed over time. 

When applied strictly, the principles of precedence first outlined by Jefferson gave rise to amendment trees that members today would consider overly restrictive. For example, the requirement that members have an opportunity to amend text proposed to be stricken and/or inserted before the actual vote to strike and/or insert said text, coupled with the stipulation that a main question could only be amended in the second-degree suggests that no more than two amendments could be pending before the Senate at the same time. In addition, the prohibition on third-degree amendments precluded members from perfecting second-degree amendments before they received a final vote. The result was a cumbersome amendment process in which senators would offer amendments to the main question ad seriatim until no other amendments were permitted or the members were satisfied with the underlying bill. Similarly, members would offer second-degree amendments ad seriatim to the pending first-degree amendment until further amendments were precluded or the members were satisfied with its text and thus ready to move on.

While today’s amendment trees are much more complex, the procedures used by members to adjudicate pending amendments remain based on the principles of precedence outlined in Jefferson's Manual. Where they differ from prior amendment trees simply reflects past senators’ conscious resolution of instances when the principles were in conflict. 

For example, the Manual states, “it is a general rule that the question first moved and seconded shall be first put. But this rule gives way to what may be called Privileged questions; and the Privileged questions are of different grades among themselves” (p. 50). Privilege is thus assigned to amendments based on one of the principles of precedence. According to the Manual, “When it is proposed to amend by inserting [striking] a paragraph or part of one, the friends of the paragraph may make it as perfect as they can by amendments, before the question is put for inserting [striking] it” (p. 61). This is because the legislative text cannot be amended more than once. With this rationale, senators began circumventing the Senate’s original prohibition on horizontal and vertical third-degree amendments. That’s why today’s amendment trees all permit either horizontal and/or vertical third-degree amendments. 


Today’s Amendment Trees

Which amendment tree the Senate follows is determined by the first amendment offered by one of its members to the measure under consideration. The letters in the charts below indicate the order in which the allowable amendments are offered. The numbers indicate the order in which those amendments are disposed of (i.e. voted on). Each branch is distinguished by the form and degree of amendment allowed to be offered at that place. 

Chart 1 is triggered when the first amendment offered is a motion to insert text.

Chart 1: Amendment to Insert

Chart 2 is triggered when the first amendment offered is a motion to strike text.

Chart 2: Amendment to Strike

Chart 3 is offered when the first amendment offered is a motion to strike and insert text.

Chart 3: Amendment to Strike and Insert (substitute for a section of a bill)

Chart 4 is triggered when the first amendment offered is a motion to strike all text after the enacting/resolving clause and to insert new text in its place (i.e. an ANS).

Chart 4: Amendment to Strike and Insert (substitute for a bill or ANS)