Algore just walkin' in there and swiping the nomination... yep, he's probably the only one who could get away with it (based on his being "cheated" in 2000). He could grab a lot of the college-age support that Obama now enjoys, ditto the Oprah crowd. Probably a bunch of Independents as well.
Hell, he's probably tougher for McCain to beat than either of the current Dems.
There's something else to consider as well: If Republicans have to sit and watch while the Democrats get a nominee do-over, knowing there's no possibility of doing the same to get rid of McCain... I can't imagine anything that would be more effective at suppressing the conservative vote.