I hope to have more on this later based on discussions with sources rather than just on pure speculation, but what follows here is just barely semi-educated guesswork backed by years of close political observation. To wit: I think the folks working against the immigration bill have momentum on their side and, if I had to bet, I would bet money that they will defeat cloture on Thursday and thus block the bill. Why? Because they secured three anti-cloture votes today that were not necessarily expected and that, if they hold them on the second cloture vote, could well provide the difference. Democrats (or Independent-caucusing-Democrats) Debbie Stabenow, Bernie Sanders and especially Evan Bayh were pleasant surprises who voted against cloture. Their stance might be indicative of the effect of the recent public opposition to cloture by the Daily Kos and by the AFL-CIO. Unless they are doing a complicated dance whereby they traded votes against cloture this time in return for other Dems (like Webb and Pryor) voting against cloture next time while these three switch in favor — which is entirely possible — then the odds actually look quite good for getting 41 votes of no (or absences) on Thursday.
If those three Dems stay where they are, the anti-amnesty forces need just five more votes. I would expect they will indeed get those five, from among the following seven senators: Republicans Bond, Burr, Brownback, Ensign, and Gregg, and Democrats Webb and Nelson. Next most likely to switch against cloture are Democrat Mark Pryor and Republican Norm Coleman, both up for re-election next year. I really, really think the anti-amnesty crowd can secure five of those nine votes.
Meanwhile, I think the only four people who could conceivably switch again from anti-cloture to pro-cloture are the three Dems (Sander/Stabenow/Bayh) and GOPer Grassley. But I think it equally likely that others could still switch from pro- to anti- — among them Dems Bingmain, Conrad, Nelson of Florida, and Levin, and Republicans Craig, Domenici, Lott, McConnell, and Murkowski.
In short, this fight ain’t over yet, not by a long shot.