Contrary to conventional wisdom, Dean's demise had nothing to do with his infamous melt-down after Iowa. Remember -- his meltdown came after he had finished third in a state where he had piled a ton of money and resources. His "official" term as front-runner for the Democratic nomination ended when the U.S. military dragged Saddam Hussein out of that hole in Iraq.
Since the economy and the war aren't the major issues it was hoped they would be, the Democrats are in a position where they must bank on a long-shot: they will put forward a candidate who can claim that he never liked Saddam Hussein (hence his voting record in the U.S. Senate), but "would have done things differently." Since the party is devoid of any ideas about how things might have been done "differently," they are left in a position where they must rely on a candidate whose only real claim to fame was that he did something heroic in Vietnam more than 30 years ago.