General Discussion

Al Franken describes it in his excellent book "Al Franken, Giant of the Senate":

"Finally, for the first time, the Democrats actually had the sixty votes we would need to move forward on health care. The bad news was that we would need every single one of those sixty votes. Which meant every single one of us had a veto. ... Still, the math was the math, and it forced us to make some tough compromises. A handful of moderate-to-conservative Democrats were opposed to the public option, which would have increased competition in the insurance market. Gone. Some floated the idea of lowering the age for Medicare to fifty-five. Hmmmm. Not a bad idea. ... Okay. Let's do it! But then Joe Lieberman announced on Face the Nation that he was against it. Gone."

Joe Lieberman (I think he was an Independent at the time) is largely to blame.