An overwhelming amount of attention has been given to Sen. Joe Lieberman (I-CT) and his decision to oppose the Medicare buy-in compromise over the past few days--but as Democrats fight tooth and nail capture one more vote on the right of their caucus to get to 60, is it possible they will lose a vote on the left?

Sen. Bernie Sanders (VT), America's only other independent senator and the most liberal member of the Senate, says he hasn't yet decided how he'll vote on the bill.

"I am now working with the White House and Senate leadership in an effort to make this bill as strong as it possibly can be," Sanders said in a statement released last night by his office. "I have not yet decided how I will vote."

Sanders plans to introduce legislation this afternoon that would create a national single-payer health care system--the kind many progressives have wanted all along--though he knows it will lose.

Liberals have railed against the Senate health care bill since the Medicare buy-in provision was removed. Marc reported yesterday that liberal voices exploded at congressional Democrats on Twitter, and Howard Dean has now said that the Senate bill would do more harm than good and should be killed.

If Democrats are to lose a liberal vote on health care in the Senate, it will likely be either Sanders, Sen. Russ Feingold (D-WI), or Sen. Roland Burris (D-IL) who defects. The Hill's Jeff Young reports that liberals have begrudgingly coalesced to support the bill after meeting with President Obama and Democratic leaders. Feingold told The Hill that he also has yet to decide how he'll vote and is waiting for the Congressional Budget Office's score before he makes up his mind. Sen. Roland Burris (D-IL) has also strongly criticized the bill, threatening to filibuster a bill without a public option.

Sanders, who defines himself politically as a Democratic socialist, is a principled liberal sometimes unafraid to go against the party's grain. Most recently, he's shown that by placing a hold on the renomination of Fed Chairman Ben Bernanke.

But he also seems realistic when it comes to health care; nor does he seem too eager to halt the overall project of health reform. Right now, he's focused primarily on expanding the role of community health centers in the Senate bill, spokesman Michael Briggs said.

In the statement last night, Sanders weighed the bill's strengths and weaknesses.

"This bill does a number of important things, but it also contains some very significant deficiencies. It provides health insurance for 31 million more Americans. It ends horrendous insurance practices like denying care for people with pre-existing conditions and increases our focus on disease prevention. It also substantially expands primary health care - an area I have focused on for years in Vermont and nationally. Its major weakness is that it does not do enough to control soaring health care costs," Sanders said.

That's a far more measured, even-handed take on the Senate bill than other progressive voices outside of Congress have given.

It looks like Sanders is open to voting yes, and that Democrats probably won't see their 60-vote coalition fall apart from the left. But, depending on how hard Sanders presses his desired changes, we may see some tweaked language on community health centers before the sausage-making is over.

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