I think Noam and Joe Trippi are both right that 2008 is not 2004--and that John Edwards won't be reprising the role of Dick Gephardt, who, in the process of torpedoing Howard Dean in four years ago, managed to sink his own candidacy as well. Which would seem to be bad news for Barack Obama, who, if '08 really were a repeat of '04, would be playing the John Kerry role and would win the nomination after the Edwards-Hillary murder-suicide.
The biggest reason '08 won't be like '04 is because Hillary Clinton is not like Howard Dean. In '04, Dean was such an unlikely--and, in retrospect, underwhelming frontrunner--that Gephardt derived no real benefit from bursting his bubble. Hillary, by contrast, is such a formidable frontrunner that if someone does manage to dent her armor, that candidate is going to look like a giant-killer--and will reap the rewards. I get the sense Obama realizes this, which is why he's been doing a better job lately of going after Hillary. But the fact is that, right now, Edwards remains the most effective Hillary-critic. And if Obama wants to beat Hillary, he's going to need to match up with Edwards in that department--and not expect Edwards to do the job for him.
Actually, the '08 race reminds me not so much of the '04 race but of professional wrestling. It was Ric Flair who used to say (often while administering a suplex or some such to an opponent): "To be the man, you gotta beat the man!" I think that applies to the '08 presidential campaign--even though the man, in this case, is a woman.