Although I'm not all that familiar with RI politics,I believe that the name Chaffee has long been a familiar one in the state.I suspect that that's part of it.Also,Chaffee is about as far from being a Republican as one can be,despite what he puts next to his name on election day.
Just look at the voting record of RI in Presidential elections.Apart from DC,I think RI gives democRAT nominees a bigger margin of victory than any other state.
That's got to be one powerful name for the dems to abandon one of their own to vote for a pubbie.
I don't know the answer and your suggestion is the closest that I've been able to get to an answer.
Thanks.