If health reform does go down to defeat, it will not be because of Republican opposition, but because of dissenting conservative Democrats and disaffected moderates in the country at large. In disappointing these people, Mr Obama has badly miscalculated.
It strikes me as terribly misguided to take the centrists seriously. As everyone keeps pointing out (e.g.), centrist Democrats have spent most of their energy gutting such provisions -- the public option, employer mandates, etc. -- as would control costs, while whining about how health care reform costs too much. I don't know if there's any good-faith interpretation of their concerns and suggestions other than that they're intellectually incoherent; even if there is, it's hard to see what this has to do with "disaffected moderates in the country at large." As Yglesias points out here, the Gang of Six collectively represents under 3% of the population of the US, with a heavy bias toward rural areas; disaffected (or other) moderates mostly live in or near cities. Besides, one supposes that the median voter depends less on special interests than rural Democratic senators representing Republican states.
I don't know how someone who's been following politics reasonably closely could think of the Senate's recent "compromises" as more than an inane and mechanical exercise in taking any policy proposal and hollowing out the parts that its advocates consider important. (Douthat had a good post on this in Feb.)