Matt's been dissing on Johnny, and though he's got some good words coming up, I have to answer him here. I take his comment that "In a lot of ways, the idea that John Edwards should be President of the United States was always a little ridiculous" as a criticism of Edwards as President rather than nominee. So let me explain why he'd make an excellent President.
The major knock on Edwards, from Matt and others, is inexperience. Sure, I'd love to have a President with the amazing wonkery powers that come from decades in politics. You definitely can't have a Bush sitting there, as his former Treasury Secretary put it, like "a blind man in a room full of deaf people." But policy stuff can be outsourced or learned without too much difficulty. What a President needs intellectually is the capacity to learn about important policy stuff quickly, and the capacity to pick out good advisors. I love the story of what Bill Clinton said after Robert Rubin and other aides explained the economy to him: "You mean to tell me that the success of my program and my reelection hinges on the Federal Reserve and a bunch of fucking bond traders?" But Clinton listened to them, and the rest is history. My judgment is that John Edwards will pass this minimal test of intelligence. Even if he doesn't know everything he should, you just put some smart Democratic wonks around him, and we'll be doing almost as well as with anybody else.
The things you can't make up for are a candidate's basic motivational dispositions. If considerations other than helping others play an excessive role in his decision-making, he'll be motivated to pick the wrong policies, no matter how much he knows. Furthermore, sheer desire to help people aids one in learning the basic descriptive facts about policy. Take it from an up-and-coming action theorist: If someone intensely desires to help the poor, believes that learning will make him more able to help the poor, and has the ability to learn, he'll do a good job of learning.
Perhaps I'm just a sucker who's fallen for Edwards' acting (and I do think he's got a lot of the actor in him), but I believe that he's intensely interested in making things better for everyone in America, especially the people who need help the most.