Jay Cost contends that the Democrats lost electoral support because they passed health care reform. Chait counters:

It's obviously true that the Democrats lost a lot of support "during the health care debate." The health care debate took about a year. My argument is that, during a period in which unemployment was rising and the Democrats controlled the entire government, Democrats would have bled support regardless of what they were debating. If they declined to carry out their campaign promises, they would have lost support.

Bernstein mostly sides with Chait.