It is a bit of a dilemma. If the GOP takes over Congress and things get better, Obama will get all the credit, just as Clinton did in 96. If the GOP takes over and things stay the same or don’t get better, Obama(supported by the media), will no doubt blame the GOP for the problems and say “well, if only the dems were still in power, things would be better”. No matter what happens he can’t lose.
If the dems stay in power and things get better Obama obviously benefits. The only real bad outcome for him is the dems stay in power and things get worse with him and the dems in total control(a la Carter in 80). But even if that happens, the media will say “see, the dems still held on to power even with all these bad things happening. If the GOP couldn’t win this year they have no chance in 2012”.
The important thing would be for the Republicans to keep the pipeline full of bills, forcing the Senate Democrats to say "No", or forcing Obama to veto bills.
I see it this way. Put people in charge that care about their country more than their ploitical futures or bank accounts. There are plenty of them out there, we just have to support them. The truth will out as the English bard said and the populace will see it.