Mixner also blamed the result on "non-white" voters.
Maine is something like 97% white.
I don't disagree that the DNC should have taken a bigger role, but frankly, Obama's efforts in VA and NJ seem to have inspired more of the teabagger vote to come out than the the cool lefty progressive vote, and I don't see any evidence that further involvement from him personally would have helped in maine--his popularity isn't necessarily transferable.
Nate Silver essentially concurs.
http://www.fivethirtyeight.com/2009/11/w…