but if he tells his Senators to support it, they run the risk of the bill coming back to bite them in the ass when it's re-election time.

They know that pending either some enormous national crisis or some huge blatant political power grab, which I don't even think Republicans would support, more and more, they already know that Bush isn't up for re-election but that they are and if they vote this bill down, they run the risk of it becoming a campaign ad against them.

"So and so voted against appropriating funds to support our troops in a time of war." etc...

I think a lot of Senators might be asking themselves if supporting Bush right now is worth their risk of losing their own careers.