Chafee has the potential to challenge Hillary, especially in New Hampshire. It's fantasy, probably, though to say he could win the nomination.
He certainly has more potential then Webb or O'Malley.
I agree that Chafee could successfully challenge Hillary in New England but the idea that he has more potential than O'Malley or Webb is absurd. O'Malley is a terrible candidate but he was an accomplished progressive governor, which gives him some credibility. Webb is also a terrible candidate but he has a "natural" base among Demosaurs.
Chafee? He was a disastrous governor. He's also a former Republican. Strangely enough, I think he'll complicate things for Sanders in New Hampshire. Affluent "latte liberals" love insurgent candidates and have the tendency to support both firebrand leftists and meek social liberals/doves.