Daily Kos on what went wrong.

Daily Kos: Political analysis and other daily rants on the state of the nation
The Dems adopted a strategy of appeasement, and then watched Bush stab all of those Democrats that supported him on the tax cut, or on the Iraq war. All early indications are that the Dem base did not turn out. In NH, Shaheen couldn't even win Manchester! Gov. Barnes of Georgia -- often talked about as a future VP nominee -- lost what seemed like a safe seat to his GOP rival.

And why should the base turn out? Many on this site (not me) were concerned about the Dems' reliance on GOTV. There was no message, many Dems were falling over themselves attempting to appear friendly to Bush's agenda. So the question was, why would the Democratic base -- those most likely to turn out in a midterm election -- go out to vote if their party's candidate was doing his (or her) best to wear Republican stripes?