Hey, we got conversation! Three Bad Fingers challenges my conclusion, and I defend here and here. This post is also relevant.

In Newsweek, Howard Fineman writes:

If there is no last-minute deal, Frist has vowed to set a vote on the nuclear option as soon this week. The "nuclear" part isn't changing the filibuster rule, but a decision by the presiding officer presumably Vice President Dick Cheney, acting in his role of Senate president that only a majority vote is needed to do so. (Normally a two-thirds "supermajority" is required to change Senate rules.) Republicans then will need just 50 votes, since Cheney can break a tie.

Thing is, there's no filibuster rule to change.

Let's just not use that word "filibuster" for a few minutes.

Standing Rules of The Senate
RULE XIX
DEBATE

1. (a) When a Senator desires to speak, he shall rise and address the Presiding Officer, and shall not proceed until he is recognized, and the Presiding Officer shall recognize the Senator who shall first address him. No Senator shall interrupt another Senator in debate without his consent, and to obtain such consent he shall first address the Presiding Officer, and no Senator shall speak more than twice upon any one question in debate on the same legislative day without leave of the Senate, which shall be determined without debate.

(b) At the conclusion of the morning hour at the beginning of a new legislative day or after the unfinished business or any pending business has first been laid before the Senate on any calendar day, and until after the duration of three hours of actual session after such business is laid down except as determined to the contrary by unanimous consent or on motion without debate, all debate shall be germane and confined to the specific question then pending before the Senate.

The very first of the standing rules of the Senate on debate says the Presiding Officer shall recognize the first Senator to address him (and so must let each and any Senator speak) and no one shall interrupt any Senator without that Senator's permission.

As I noted the other day, Senate rules and procedures are not the same things. The procedures are agreements on how the requirements of the rules are to be met. Rules are like a skeleton that establishes the basic form of things, where procedures are the muscle tissue (and, sadly, the fat) of the living system. Our policy disputes are like, "shall we bulk up, shall we trim down, are we basketball or hockey players?" They should not be about, "should we reduce our bone mass?"

Anyway, there are rules governing how Senate rules can be changed. It requires two-thirds of voting Senators.

Standing Rules of The Senate
RULE XXII
PRECEDENCE OF MOTIONS

2. Notwithstanding the provisions of rule II or rule IV or any other rule of the Senate, at any time a motion signed by sixteen Senators, to bring to a close the debate upon any measure, motion, other matter pending before the Senate, or the unfinished business, is presented to the Senate, the Presiding Officer, or clerk at the direction of the Presiding Officer, shall at once state the motion to the Senate, and one hour after the Senate meets on the following calendar day but one, he shall lay the motion before the Senate and direct that the clerk call the roll, and upon the ascertainment that a quorum is present, the Presiding Officer shall, without debate, submit to the Senate by a yea-and-nay vote the question:

"Is it the sense of the Senate that the debate shall be brought to a close?" And if that question shall be decided in the affirmative by three-fifths of the Senators duly chosen and sworn -- except on a measure or motion to amend the Senate rules, in which case the necessary affirmative vote shall be two-thirds of the Senators present and voting -- then said measure, motion, or other matter pending before the Senate, or the unfinished business, shall be the unfinished business to the exclusion of all other business until disposed of.

You see? We don't have a filibuster rule, we have a cloture rule.

Understand that there is no judgment involved here. The rule is very explicit...three-fifths (60) for cloture, two thirds (66) to change the rules. And the rules have, indeed, been changed. In 1917, a rule change provided a method to forcibly end debate on the Senate floor...it took a two-thirds majority. In 1975 that was cut back to a three-fifths majority. So it can be done.

It just takes two thirds of the Senate to do so.

So Senator Frist's "nuclear option" isn't really an option at all.