Order Code RS22854
April 2, 2008
Filling the Amendment Tree in the Senate
Christopher M. Davis
Analyst on the Congress and Legislative Process
Government and Finance Division
Summary
“Amendment trees” are charts that illustrate certain principles of precedence which
guide the Senate amendment process. When all of the amendments permitted
simultaneously by these principles have been offered and are pending, an amendment
tree is said to be “filled,” and no additional amendments may be offered until one or
more of those pending is disposed of or laid aside. Given that the presiding officer
traditionally affords the Senate majority leader or his designee priority over all others
in being recognized, a majority leader can repeatedly secure recognition and “fill the
amendment tree” himself by sequentially offering all of the amendments permitted under
applicable circumstances. By doing so, a leader can “freeze” the amendment process
in place, blocking additional floor amendments, at least temporarily. A majority leader
might “fill the tree” in this way to prevent the offering of or voting on of non-germane
amendments, to try speed consideration of a measure, or to control the subject or
sequence of amendments that may be offered.
Background on the Amendment Trees
The “amendment trees” have developed over decades of Senate practice as a way of
visualizing certain principles of precedence that govern the offering of, and voting on,
amendments in the chamber. These principles of precedence are reflected in four
amendment tree charts published in the official compilation of Senate precedents which
depict the maximum number and type of amendments that may be offered and
simultaneously pending under various circumstances during consideration of a bill.1
Which of the four amendment tree charts will be applicable at a given point during
consideration of a measure is dictated by the form of the first amendment that is offered
— be it a motion to insert, to strike, to strike and insert, or in the nature of a substitute.
1 Floyd M. Riddick and Alan S. Frumin, Riddick’s Senate Procedure: Precedents and Practices,
101st Cong., 1st sess., S.Doc. 101-28 (Washington: GPO, 1992), pp. 74-89. See also CRS Report
98-853, The Amending Process in the Senate, by Betsy Palmer.

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An amendment tree is said to be “filled” when all of the amendments permitted by
these principles of precedence have been offered and are pending. Depending on which
tree applies in a given floor situation, an amendment tree might be filled by as few as
three, or as many as 11 amendments. When an amendment tree is full, the amendment
process is, in effect, “frozen” — no additional floor amendments may be offered until
action is taken to dispose of one or more of those already pending. Pending amendments
might be disposed of by being voted upon, withdrawn by their sponsor, or tabled. The
Senate might also lay aside a pending amendment or amendment tree by unanimous
consent so that a Senator may offer another amendment, notwithstanding those pending.
Recognition and the Senate Majority Leader
Under paragraph 1(a) of Senate Rule XIX, the Presiding Officer “shall recognize the
Senator who shall first address him.” In keeping with Rule XIX, Senators offer
amendments to a pending bill in the order they obtain recognition to do so. Under
traditions and practices observed since at least the late 1930s, however, “in the event that
several Senators seek recognition simultaneously, priority of recognition shall be accorded
the Majority Leader and Minority Leader, the majority [bill] manager, and the minority
manager, in that order.”2 This priority in recognition afforded the majority leader or his
designee is relevant to the amendment tree because the order of recognition can affect
opportunities in the amendment process.
When a Senator has offered an amendment, he or she has the right to withdraw or
modify the amendment. After action has been taken on the amendment, such as ordering
the yeas and nays, however, its author loses the unilateral right to withdraw or modify it,
but gains the right to amend it.3 Accordingly, if a Senator offering an amendment on
which action has been taken can again secure recognition, he or she may offer an
amendment to their own amendment, so long as the new amendment complies with the
principles of precedence described above.
Thus, while any Senator (or group of Senators acting in concert) might potentially
“fill the amendment tree,” the custom of granting the majority leader or designee priority
recognition means that a determined majority leader will always be recognized before
other Senators, and, as a result, the majority leader alone is guaranteed the ability to fill
the amendment tree by being repeatedly recognized in turn to offer amendments to a
pending measure (and to their own amendments) until no more are in order.
Possible Strategic Reasons For “Filling the Tree”
A Senator, particularly the majority leader, might pursue a strategy of “filling the
amendment tree” for several reasons, including
! preventing non-germane (and perhaps politically controversial)
amendments to a measure from being offered or voted upon;
2 Ibid., p. 1093.
3 “Action” includes ordering the yeas and nays on the amendment, adopting, rejecting, or tabling
it, amending it, or entering into a unanimous consent request specific to that amendment.

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! attempting to expedite overall Senate consideration of legislation by
limiting the overall number of amendments offered;
! obtaining advantage in the negotiation of a unanimous consent request
for the further consideration of a measure;
! obtaining the first recorded vote on a policy provision in the exact form
desired; or
! instituting some measure of leadership control over the subject or
sequence of floor amendments offered.
After filling an amendment tree, the majority leader may file a cloture petition, either
on a pending amendment or on the underlying measure. If cloture is invoked on the
measure, not only does it establish a 30-hour limit for further consideration of the bill,
it limits amendments that may be offered to those that are germane and any pending non-
germane amendments fall. By keeping a tree full until cloture is invoked, a majority
leader may be able to prevent action on a pending non-germane amendment, prevent all
non-germane amendments from being offered, or limit the consideration of additional
amendments altogether.
A majority leader might also fill the tree in an effort to require the Senate to
complete action on an amendment tree that includes an amendment in the nature of a
substitute, or a substitute for a portion of a measure. Once a substitute for a measure or
a section has been adopted, no further amendments to that text are in order because it is
not permitted to amend only text that has previously been amended.
Finally, a leader might fill the tree in an attempt to allow only those amendments
acceptable to him to be offered to a measure. This could be accomplished by filling an
entire tree and agreeing to a unanimous consent request to lay aside a pending amendment
only for the offering of favored amendments. A majority leader might also fill some, but
not all of the available limbs on an amendment tree, and use his right of first recognition
to call up and offer amendments that he finds acceptable — possibly including filed
amendments authored by other Senators.
Implication of Filled Trees
As noted above, when a majority leader “fills the amendment tree,” he “freezes” the
amendment process in place, limiting opportunities for other Senators to offer
amendments while the tree remains pending, and potentially after the amendments are
adopted as well. While the leader’s ability to fill the tree gives him at least some
temporary control over the Senate floor, it also means that floor proceedings are largely
“frozen” for him as well. Unless the Senate chooses to invoke cloture, a measure is
regulated by a statute which limits overall debate, or the majority leader is able to
negotiate a unanimous consent agreement regulating the further consideration of the
legislation, a majority leader is subject to the same procedural stalemate as other Senators.
In addition, the tactic of blocking amendment opportunities in a chamber which by
long tradition places few limits on the ability of individual Senators to amend legislation
may create a negative reaction which impairs a majority leader’s future ability to manage

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the Senate floor. These considerations may help explain why filling the amendment tree
has been a visible and often politically-charged occurrence even though it has been
comparatively infrequent.