Late in the negotiations over the public option, a group of five conservative Democrats and five more-liberal Democrats seemed near to an unexpectedly smart compromise: Allow adults over 55 to buy into Medicare. This idea had a couple of different virtues: For one, it opened an effective and cheap program up to a group of Americans who often have the most trouble finding affordable insurance. For another, the Congressional Budget Office has said this policy would improve Medicare's finances by bringing healthier, younger applicants into the risk pool. Oh, and it's wildly popular with liberals, who want to see Medicare offered as an option to more people, and since Medicare is already up and running, it could've been implemented rapidly.
But Lieberman killed it. It was never really clear why. He'd been invited to the meetings where the compromise was developed, but he'd skipped them. He'd supported the idea when he ran for president with Al Gore, and he'd reaffirmed that support three months prior to its emergence in the health-care debate during an interview with the editorial board of the Connecticut Post. But now that it was on the table, he seemed to be groping for reasons to oppose it. About the best he managed was that it was "duplicative," which was about as nonsensical a position as could be imagined. Nevertheless, he swore to filibuster the bill if the buy-in option was added. The proposal was duly removed.
http://voices.washingtonpost.com/ezra-klein/2010/11/how_joe_lieberman_helped_the_d.html?wpisrc=nl_pmpolitics