Major Democratic losses were guaranteed by the failure to deliver a significant improvement in job markets. To have avoided these losses, Obama would have had to have a stronger economic program -- above all, a bigger stimulus. Could he have gotten one? If not, the White House was a poisoned chalice from the beginning. But the point is that he didn’t try. To the extent that Democrats do worse even than the economy explains, one can point to a number of factors. Given that the stimulus was inadequate —- which was obvious early on —- Obama could have tried to warn Americans of a long hard road ahead, and placed blame on Republicans; instead, the WH kept pretending that things were going swimmingly, never once acknowledging that the original plan wasn’t sufficient (they still haven’t).
This seems fair, especially the poisoned chalice bit (which I recall we all feared from the first), but it's also true that if doing our best and hoping for the best was the best we could do there was certainly no reason not to hammer the Republicans harder from the beginning as the villains in this narrative to mitigate somewhat this insanely mis-aimed punitive mid-term, especially given how clear it was and how quickly it was clear that the Republicans had no intention of responding to chirpy bipartisan noises in any kind of productive way anyway.