Of all the mainstream candidates for the Democratic Party nomination, John Edwards at least gave serious lip-service to progressive issues. His insistent focus on the rampant poverty afflicting America's majority under-class was the bane of elite opinion in the corporate media universe, and made it clear almost from the start that his campaign was doomed. You see Edwards failed to grasp that public opinion and public policy in this country do not align. So while his positions were (at least superficially) in accord with public opinion on issues such as the need for single-payer universal health-care, ending the criminal occupation of Iraq, reigning in the so-called "free-trade" agreements, and reforming tax policies which further enriched the wealthy, these positions were anathema to the elite class who actually implement and influence US foreign and domestic policy. Thus he never had a prayer, despite the fact that he polled better than every Democratic challenger against the Republicans currently in the race.
For more on Edward's demise, I found
this gem from Weldon Berger over at BTC News, though I must add that his advice to "vote Obama" is clearly absurd.