I will say this...
While a GOP Senator he was the only one to vote against the Iraq War, supported gay marriage, and was an environmentalist advocate. As Independent Governor he signed gay marriage into law, passed a controversial pension reform law, and decided not to run for a second term and changed his affiliation to Democrat (the really only specific instance people gave of why he was unpopular was because he called the state Christmas tree a Holiday tree... Which actually started under his Republican predecessor). He's also good friends with Obama.
But he doesn't even stand a chance in RI.
As much as its fun to make fun of Chafee, his record really isn't bad. It's just that he has no name recognition, is unpopular at home, and faces the Hillary Steamroller. Being an older white guy doesn't give him any pizazz either. Sanders is at least Jewish.