While Edwards may not have Obama's charisma or Clinton's machine, I don't think he has the kind of negatives that either Obama or Clinton do which might energize the far-right to get out and vote in opposition.   Even if Clinton or Obama won the White House, if those who hate or fear them are mobilized to vote, it could threaten or lessen the Democrats' victories in Congressional and Gubernatorial races.

Clinton's "negatives" are 1) she's a woman 2) she's a Clinton, 3) she's now seen as a northeastern urban candidate, and 4) her persona is viewed by too many as "cold" or "bitchy."   As undeserved as any of those perceptions or prejudices may be, I can't see her taking any southern states except maybe Florida or Virginia or Arkansas. But a lot of people seem to hate her passionately, dread the Bush-Clinton dynasty thing, or just abhor the idea of a female President.

Obama's "negatives" are 1) he's "black," 2) he's also seen as an urban Yankee, 3) his middle name is Hussein and his last name "sounds like Osama" and he once attended a Muslim school [aka "madrasa"].    These are the things that may mobilize a lot of racists, religious bigots, die-hard Southerners, and just people who are still traumatized by "the war on terror" to get their butts out to the polls to vote against him -- and his party.   His charisma could still sweep him into the White House, but with no "coat tails."

Edwards, according to polls, has very low negatives.   I think he faces a real uphill battle to win his party's nomination -- but, as with Kucinich, that battle is as much with the mainstream media as with the American people.    If he can win the nomination, I think he is not only the most electable Democrat but the one who might have the longest coattails, if only because few people either fear or hate him,