Kevin Drum documents the disconnect.
To recap, voters like the Democrats more than the Republicans. They think Democrats share their values and would rather actually see them in charge. But somebody's got to pay for not fixing the Bush economic collapse in 18 months, and that somebody is going to be the Democrats...because they're in charge.
The Republicans don't have to run on anything. "They're not the Democrats" is all it takes, apparently.
They're taking it out on the Dems. Logic goes like this: "Democrats have had 18 months to fix this economy and they've failed. There's a 99.999% chance the Republicans will make it worse, but you know, hope and change."