WASHINGTON -- Nebraska Sen. Ben Nelson (D-NE) has followed the fastidious Sen. Joe Lieberman (I-CT) in withdrawing his support from the Senate health care compromise, which jettisoned the public insurance option in favor of a Medicare buy-in program for people 55 years and up.

"I am concerned that it’s the forerunner of single payer, the ultimate single-payer plan, maybe even more directly than the public option," Nelson said on Sunday in an appearance on CBS' "Face The Nation."

The Nebraskan also declared he's concerned about the potential costs of the provision.

Nelson and Lieberman both appeared on the program, and said that the Medicare expansion provision doesn't have 60 votes in the Senate.

It bears pointing out that they are the only two non-Republican members of the upper chamber that have thus far opposed it -- with their support, there would be 60.

Nelson had no problems with the bill as it stood last Wednesday. "I'm not aware of anything that was raising serious objections about it," he said. "I think it was about, 'Well, that sounds okay, let's see how it scores.'" But he started singing a different tune after the Senator from Connecticut pulled back abruptly.

A November poll carried out by Research 2000 found that Nebraskan voters favored the public option -- which Nelson's defiance compelled the Democratic leadership to remove -- by 46 to 44 percent. In Connecticut, the provision was even more popular, with 56 percent supporting it and 37 opposing, according to Quinnipiac.

While Lieberman's opposition to the new compromise is resolute and unequivocal, Nelson's is less staunch, signaling that he might still be won with tweaks.

Nelson's demands are unclear, and with the nature of the bill constantly changing, it's remains to be seen whether the bill will achieve the goals of extending coverage and bending the cost curve if his concerns, along with Lieberman's, are placated.

Nelson suffered a setback last week when an amendment he co-sponsored that would more strongly restrict abortion rights was struck down.

The absence of even one of their votes creates serious problems for the Democratic leadership, as none of the 40 Republican Senators are at all likely to back it. Their options are to either water down the reforms further or use the parliamentary maneuver known as reconciliation, which might change the shape of the legislation but would allow it to pass with 51 votes.

This video is from CBS' Face the Nation, broadcast Dec. 13, 2009.

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