Edwards is the most left leaning of the viable candidates, and the most left wing of any of the candidates besides Kucinich. He has to temper public displays of support for MM though, since if he gets the Democratic nomination (which he has a fair chance at doing) he still has to play to a more moderate general electorate. Saying "yeah, MM is great" right now could harm his chances down the road.

Unlike guys like Paul and Kucinich (the REALLY loony ones -- Keys and Gravel), guys like Edwards and Obama can't just say what they really think most of the time.

EDIT: couple of typos.