I've seen many writers (including Atrios and Yglesias, for starters) criticizing Democrats for not having a coherent message going into the midterm elections. And I'd agree -- Democrats don't have a coherent message.
But, of course, this really doesn't matter. Democrats didn't have a coherent message going into 2006, either, and they took over both chambers. And the Republicans stand to do quite well this year without having much of a coherent message. The "message" is just a media narrative and will largely be written after the fact anyway. Does anyone really think that the Democrats can overcome the problems of running on a weak economy with their president's approval ratings in the 40s by coming up with the right words for their campaign banners?