In response to Joe Lieberman's concerns and pressure from the White House to negotiate a deal quickly, Senate Democrats have dropped the Medicare buy-in that they'd negotiated in exchange for dropping the public option. Progressives had long pushed the line that the most liberal legislators might refuse to vote for a bill without a public option or some significant concession to replace it, but at least in the Senate, this was never very convincing: Liberals were almost certain to favor any sort expansion of insurance, meaning moderates always held the power. Now, hated as he is by ardent liberals, Lieberman basically holds the option to make or break health care — or change the deal to suit his whims. In other words, right now, Senate health care negotiations bear a close resemblance to this:
Hat tip to Patterico's Karl for the reference.