I'd suggest that the waning public support has more to do with the ongoing FUD campaign by Republicans and the watering down of the whole idea. With their total Nyet! stance, repubs put a few so called conservative Senate Democrats into the catbird seat, who forced the kind of change Repubs could actually agree with- giveaways to big healthcare. But they don't have to. They get the best of both worlds- favors to their usual contributors and plausible deniability all in one.
Current methods of healthcare delivery cost more and more all the time while covering fewer and fewer people. If we hold the current course, we'll experience systemic failure in not too many more years. Just the way it is. And that's apparently fine by Republicans and their supporters- they had no problem at all allowing near collapse of the banking system, after all...
With some luck, the compromise version will be more like the HOR bill, with a public option and actual cost controls. If, as Righties claim, that private enterprise can do it better, it seems to me that they'd jump at the chance to prove it, drive the public option into the dirt with their much vaunted better way of doing things... But they're not, not at all. Why is that?
Maybe it's because they're knowingly peddling lies and have been for decades...