I think Obama and the "mainstream" media are making a big mistake by going after Joe the Plumber. I know it's reflexive and they just can't help destroying people who expose and decry their Marxist redistribution schemes, but I think Joe the Plumber will get a lot of sympathy from Obama's must-win voting blocs.
William Graham Sumner wrote, regarding FDR's New Deal:
They are always under the dominion of the superstition of government, and forgetting that a government produces nothing at all, they leave out of sight the first fact to be remembered in all social discussion — that the state cannot get a cent for any man without taking it from some other man, and this latter must be a man who has produced and saved it. This latter is the Forgotten Man.
I don't think people will forget Joe the Plumber for a while.
The MSM is too busy to look into Obama's past, but they're investigating Joe the Plumber. Good question by Allahpundit about Joe's lack of a plumbing license:
Exit question: The law’s the law and it is, after all, his own fault for not having the papers he needs. If, say, an illegal alien had asked McCain a tough question and some righty media source responded by bringing his status to light, would the left feel the same way?