I think moderate Vermont voters are going to think twice about sending Sanders to the Senate. Even in states with more Senators than Reps I think voters are cognizant of the different demands of the respective bodies (Vermont having a very educated voter pool).
With Douglas, they get a Senator who would be in the majority and quite possibly get good committee assignments and plenty of pork for Vermont. In Sanders, they get an independent who has to be protected by a minority party-- which is unlikely to place his needs above their own members.
That is why Douglas can win (and why Chafee is still a Republican and why he's going to win in RI). Sanders is not Senate material and Douglas is, plain and simple... leftists are in la-la land with this one.
What leftists? I find it hard to believe that Vermonters are going to make such a dispassionate analyisis in favour of Douglas with Theocracy staring them in the face.