Anyone remember Rockey Vaccarella?
He was a GOP operative who pretended to be a "Katrina Victim" driving his trailer from New Orleans to Washington DC to give Bush a photo op. They tried to sell him as a regular guy surprised to be taken into the White House at the end of his pilgrimage, and the press ate it up before they realized who he really was, but didn't bother covering the deceit in any signifcant way after the fact.
I can't help but think that Joe the Plumber smells a bit like Rockey. I don't think he helps McCain much anyway, but if this guy turns out to be a fraud... well, probably nothing more will happen really, much as I wish a Republican could receive his comeuppance every now and again.