The House has already passed legislation requiring troops to be withdrawn by Sept. 1, 2008. The Senate vote assured that the Democratic-controlled Congress would send Bush legislation later this spring that calls for a change in war policy. A veto is a certainty, presuming the president follows through.
That would put the onus back on the Democrats, who would have to decide how long they wanted to extend the test of wills in the face of what are likely to be increasingly urgent statements from the administration that the money is needed for troops in the war zone.
Democrats just won an election largely on the basis that they would change course on Iraq. The President won't just be vetoing legislation, he'll be going against the will of most of the country that his failed war be brought to an end.
I'm sure there are people around Bush that are blowing smoke up his butt and playing to his short guy syndrome but the American people won't be as easily dazzled by bullshit this time around. Add to that the large number of Republican Senators up for re-election and I think it's fair to say that a funding crisis would largely put the onus on Bush and the Republican party to join the rest of America on this issue.
(I see Gordo voted with the angels on this one. I don't care. If this weren't an election cycle I haven't the slightest doubt he'd be on the other side. When it comes to principle he's the exact opposite of the principled tradition of Oregon Senators and no heir to Mark Hatfield.)