Reply #7: This story lists 43 sure votes in Senate for Public Option with work perhaps 50 can be achieved:

[WI_DEM]

(but it will be tough)
44. Tim Johnson (SD). Appeared to commit to the plan over the weekend. Should be regarded as a highly likely 'yes' vote.
45. Robert Byrd (WV). Has yet to take a position publicly, probably because he's been ill. But Byrd is generally pretty liberal on economic issues, and his colleague (Jay Rockefeller) is a vociferous supporter of the public plan. The potential barrier here, as in Kennedy's case, is likely Byrd's health rather than any philosophical concerns he has about the plan.
46. Amy Klobuchar (MN). Howard Dean's website lists her as a supporter. She's been decidedly more ambiguous in e-mails to constitutents, and Minnesota has lots of skin in the health care game in various forms. Still -- although Klobuchar is not as liberal as you might expect from a Minnesota Democrat -- this seems to me like an eminently whippable yea vote.
47. Ron Wyden (OR). Wyden's indifference to the public option is a little odd -- he's ordinarily quite liberal -- and may reflect his desire to promote his own health care alternative. Once it came time to vote on the actual, non-Wyden bill, I'd expect him to vote yes on the public option.
48. Herb Kohl (WI). Ostensibly supports the public option but with a lot of caveats: that it be "bipartisan", etc. Realistically, any public option that the Senate is considering is likely to be fairly watered down, moving Kohl into the probable yea vote category. But the co-ops concept might also be alluring to him.

Now, here are the senators that Bowers lists as maybes but who I think would be relatively unlikely to vote for the public plan. Not included here are Joe Lieberman and Susan Collins, who he lists as definite no's.

Mary Landrieu (LA). Other sources have her as a 'no'. She may be hedging a bit in constituent e-mails, but given a straight up-or-down vote on the public option, her vote seems highly unlikely.
Johnny Isakson (GA). Republican who is moderate on health care issues. Open Left lists him as a "maybe" based on what I think is a very optimistic read of a statement he made in June. Also, Isakson (along with all other Republicans but Olympia Snowe) sent a letter to the President stipulating his opposition to the public plan. Very little chance he'd vote for a public option.
Kent Conrad (ND). Given that he's probably done more than any other senator to hurt the public option, I don't really see him coming up big for the plan in the clutch.
Ben Nelson (NE). Generally the most conservative Democrat in the Senate, Nelson came out against the public option early on but has since hedged a bit. I don't know that Nelson would vote to filibuster a health care bill on final passage if it happened to include a public option. But, given the opportunity to take a straight up-or-down vote on the provision without bearing the burden of potentially killing health care reform (e.g. if an amendment on the public option had been proposed), I don't think a 'yes' vote is likely.
Evan Bayh (IN). Similar story to Nelson. He's been voting very conservatively (even relative to normal) this year.
Tom Carper (DE). Fairly conservative, and very corporatist Democrat. He takes a lot of money from the insurance lobby and there are also a lot of insurance jobs in his state. Seems to want co-ops instead.
Mark Warner (VA). Takes a ton of money from the industry. Our regression model regarded him as a very unlikely 'yes' vote. Has been somewhat ducking making a commitment on the issue, but some constituent communications suggest he'd much prefer the co-ops plan.

That leaves seven senators who I suspect are the true swing votes in a 50-vote environment. The Democrats would need at least two of these, and possibly as many as 4-5 depending on the health of Byrd and Kennedy and whether someone like Feinstein or Kohl ended up voting against the public plan.

Blanche Lincoln (AR). She's been all over the board on the public option. I don't know if anyone can say with confidence how she'd vote until they take the roll call.
Mark Pryor (AR). Been receiving less scrutiny than Lincoln since he's not up for re-election, but his position has been just as ambiguous.
Mark Begich (AK). Here's a guy who I suspect has fairly liberal instincts and doesn't take a lot of PAC money but is obviously in a very conservative/libertarianish state. Probably among the more gettable of the swing votes.
Jon Tester (MT). Largely the same story as Begich, although he's a bit more of a populist.
Max Baucus (MT). Public statements suggest he supports the public option in principle but he obviously hasn't done very much to move it along in practice. Common sense would dictate that he'd be unlikely to vote for a public option if it wasn't in the bill that came out of the Finance Committee. On the other hand, it's not out of the question that he'd want to save face with some of his liberal critics.
Bill Nelson (FL). "Not even his hairdresser knows," according to the Huffington Post.
Olympia Snowe (ME). Would probably vote for a public option that had a 'trigger' and vote against it otherwise.