One story that doesn't get told often enough when it comes to the potential doom for Democrats this fall is that there really just aren't that many Obama voters shifting toward the GOP. Our last national poll found only 8% of people who voted Democratic for President in 2008 planning to go Republican for Congress in 2010. If this ends up being a huge Republican year- and it may well be- it's going to have a lot more to do with Democrats staying home than Obama voters abandoning the party.
There's not much doubt what's driving those few people who are shifting from Obama to the GOP: the economy. 72% of them think the economy's gotten worse since Obama took office, and 64% of them say their own personal economic situation has worsened. They don't have much optimism looking forward either- only 11% think the overall economy will be better by November and just 7% think their own situations will improve.
Democrats will start doing better when voters start to really feel the recession's on the way out- but mostly they'll start doing better when they can find a way to get their own voters motivated.