State of the Health Care Bill

Ta-Nahesi Coates (a daily read of mine) posted his discussion with Ezra Klein about the status of the Health Care bill now that Kennedy's Senate seat has been lost. Klein does an excellent job of explaining why the (Senate version of the) bill was (and still is) worth supporting. While Klein describes it as "intellectually honest" for progressives to admit that we truly wish for a single-payer system and that the current bill isn't really what we'd dreamed of, he rightly insists that the potential improvements to our present system included in the bill are too great for us to pass up.

Although my own insurance situation will not be affected either way (bill or no bill), I can't shake the feeling that we are missing a historic opportunity to accomplish something momentous in terms of social justice and economic fairness.
Perhaps most frustrating is the thought that the Democrats are on the verge of dropping this completely simply because their huge majority in the Senate was diminished by just one seat. One f'n seat! They still have 59 seats in their caucus. Maybe I'm overestimating the discipline of the congressional GOP, but I'm pretty confident that if they had a 59 seat majority in the Senate, with an insane majority in the House, not to mention a doctrinaire Republican in the White House, and that if they were then on the verge of passing legislation that was pretty much a pillar of their party's agenda for a generation or two (say tax code reform, for example), they would not hesitate to ram it through. They would succeed. Sure, some Senate Democrats would threaten to filibuster, but in the end, they would pass their bill, the President would sign it, and they would all celebrate together at parties with their mistresses, while drinking bourbon, and joking about how easy it all was.
Why can't the Democrats accomplish things the same way? Is it a matter of will? Are they just a bunch of cowards? Or is it just that a significant proportion of elected Democrats aren't committed to social democratic or progressive ideals to begin with? If so, what the eff are they doing in our party?