WHY IS EDWARDS STRUGGLING? This, from Garance's examination of why Edwards has failed to gain traction among low-income and minority voters, strikes me as a smart point:
Democrats are working with two change axes in this race -- a demographic one and a policy one. Edwards has been freer to propose more forthrightly liberal policies, such as his anti-poverty agenda, because he is the demographic status quo, while Clinton and Obama have taken a more cautious approach as candidates as a way of balancing the change they represent demographically.
In other words, Edwards, being a white, Southern male, can be more forthrightly liberal than Hillary Clinton. Since the optics of his candidacy don't pose a threat, he can imbue the policies of his campaign with more radicalism. For many white, male, liberal types, that makes him the more transformative candidate. For many non-white, non-male, liberal types, it would be substantially more radical to elevate a non-white or non-male to the presidency. There are compelling cases to be made on both sides.
That said, I don't think you can attribute Edwards' thin support entirely to such dynamics. Part of his problem, from the beginning, has been that the media has treated him as yesterday's news. How many recent magazine covers has Obama received? Clinton? Edwards? Part of his problem has been that he's run, at times, a bad campaign, and made more news for missteps than for triumphs. And part has been that he's gotten strangely little coverage for his strengths, such as an apparently enduring lead in Iowa (though it looks like Hillary is closing in), substantial strength in general election match-up polls, and a compelling and detailed political platform. But at the end of the day, one of the reasons people don't like yesterday's product is the simple belief that it belongs to yesterday, and that, more than anything else, strikes me as the perception Edwards is battling.