Nate Silver and Jonathan Bernstein have good follow-up posts on this conservative idea that health care reform is the main reason why Democrats are in danger of losing the House. Let me add a couple thoughts.
First, to show that an issue is unpopular for Democrats does not mean that the issue in question, rather than the economy, is the cause of the party's woes. One of the things that happens during a terrible economy is that people turn against the president and his program. So, no question, people think Obama has expanded government too much. But during the 1982 recession, people thought Ronald reagan's anti-government program was too right-wing. And during the 1991 recession, people thought George H.W. Bush was doing nothing. Whatever the president does is going to be seen as too far to the right, too far to the left, or too little. So to show that a particular issue polls badly for the president during a recession does not prove that the president would be in good shape if he had a didfferent position on that issue.
Second, the argument that health care is the Democrats' political problem does not think very rigorously about the alternative. Actually, there are two conservative arguments here. The first, made energetically by right-wingers last Spring, was that Democrats would be wise to abandon health care reform even after passing it through both houses. That was a transparently ridiculous argument.
The more plausible case would be that they should never have taken up health care in the first place, and used their time pushing some kind of economic stimulus issue. I still have trouble buying this case. There's an issue of keeping faith with the base. It's also the case that the public may have made problems with Obama's plan, but it never wanted to do nothing on health care. Indeed, Republicans made strenuous efforts to convince the public that they merely wanted to start over and craft a better health care plan. It was a dirty lie to accuse them of favoring stalemate. This suggests that doing nothing on health care would also have alienated large swaths of the public.
Moreover, a recent Gallup poll shows that Democrats fare about evenly (+1) versus Republicans on health care -- it's one of the only issues where they don't have a disadvantage:
At the same time Americans trust republicans a lot more on the economy. None of this is reason to think spending less time on health care and more on "the economy" -- where it's not clear the Democrats could have passed anything substantial -- would have helped.