The bill comes to the Senate floor. There may be a unanimous consent agreement; but it won't, I'm pretty sure, restrict the amendments that can be offered.

During floor proceedings, a GOP senator - even better, old Joe Lieberman! - offers an amendment to the substitute striking the Proviso.

At this stage, the Dem leadership has a choice: it can either allow the amendment to be debate and voted on, or Uncle Harry can make a motion to table.

The MTT passes on a simple majority, is nondebatable, and, if passed, kills the amendment.

The advantage to the majority leadership of using the MTT? It's a power move (the leadership taking the initiative); it gets rid of the amendment straight away; it betokens leadership confidence in the accuracy of its count (and, by extension, in its own competence generally).

How about that count, though? The maximum Dem strength would be 49 (ie, less Lieberman - presumed voting with the GOP - and Johnson); a full GOP turnout would give them 50.

Ties could be broken by You Know Who.

So - to win the MTT, the Dems need to switch a net single vote.

How likely is it?

Well, we know that, at the time that Warner-Levin (S 470) came to a vote (on cloture on the motion to proceed),

• W-L was short of 60 votes (otherwise cloture on the MTP would have passed with the votes of GOP supporters of W-L, Harry would have filled the tree, and the same bunch who voted for cloture on the MTP would have voted for cloture on the bill); and

• Gregg (pledging no defunding) had more than 60 (Novak said 70).

Now, included in the W-L text was a paragraph, almost identical to that in Gregg, pledging no defunding.

(The Dem leadership was happy to go along with this as a quid pro quo for registering Senate dissent from the surge; but not as a stand-alone.)

Which means that at least 60, and perhaps 70, senators were prepared to vote against defunding.

So - going back to our Murtha Proviso example, it seems on the face of it unlikely that the Dems will muster their nominal strength (ie 49), let alone win a MTT on an amendment to strike the Proviso.

But - let's take a look at the W-L defunding text:

the Congress should not take any action that will endanger United States military forces in the field, including the elimination or reduction of funds for troops in the field, as such action with respect to funding would undermine their safety or harm their effectiveness in pursuing their assigned missions;

How many Dem senators will argue that that text is compatible with the Proviso because the Proviso would not undermine their safety or harm their effectiveness in pursuing their assigned missions?
They may go on offense and suggest that the Proviso actually enhances both safety and effectiveness by taking steps to avoid undertrained or underequipped forces into theater.

But that argument only goes so far: the GOP will not confine its challenge to W-L Dem supporters on verbal niceties - it'll suggest that they were prepared to offer funding assurances once which now they were not.

Plus - depending on the scope of the Proviso (from which we're abstracting for the purpose of this test exercise), it may prevent the deployment of units the absence of which may put troops in the field in danger.

And - the GOP will undoubted argue, at a more political level, that this is the very intention of the Proviso: to present the WH with the choice of deliberately endangering the troops or having to withdraw from Iraq.

Enough of the politics!

Let's say Harry makes the MTT and it's rejected. Normally, the amendment to strike would pass on a voice vote. In the recent past, Harry has not allowed that to happen (details escape me for the moment); but, I'm fairly sure (!) that, the amendment to strike will be the pending business whenever the bill comes back to the floor.

(In other words, Harry would have to allow a vote on it, but, like DeLay and the Medicare bill vote, he'd have time to twist arms. More time than DeLay had, quite possibly.

But who's counting?)

So - leaving aside for the sake of this exercise the possibility of vote-switching between the MTT vote and the vote on the amendment, a simple majority will see the Proviso excised.

Now, let's consider cloture.

Suppose the MTT on the amendment to strike passes, and the amendment is thereby kiboshed.

The GOP would, no doubt, prefer not to filibuster (in the modern sense) the bill itself, because that just lets in Dem claims that they are failing to support the troops!

But, if the substitute as carefully crafted by Byrd and Co is good to go, they will have nothing but the bill to filibuster.

End of exercise.

That's just a rough and ready (mostly, rough) illustration of the sort of planning a kibitzer would need to do to try and keep in touch with - for preference, ahead of - the Congressional game as it proceeds.

As new information comes in, so the plan would get refined.

(Reference Chris's excellent proposal to explore the possibility of a campaign in favor of the Proviso.)