With 15% undecided, it seems very possible that Clinton reaches 60%. Also, what's going on with the governor's race? Why is Minter running so far behind Clinton?
Minter is associated with the unpopular incumbent, Pete Shumlin, while Phil Scott is well-known as a moderate who has been an opponent of Shumlin, and also for his construction business in the state.
Zuckerman has bad relations with the state Democratic Party, and Brock has the advantage of having been the Republican gubernatorial nominee in 2012 (so, voter's remorse is a factor here) and that Scott/Brock are essentially running a ticket. Even so, Brock may be too obscure to overcome the state's natural lean.
EDIT: As for the high presidential undecided, Vermont counts all write-in votes, regardless of whether the candidates are registered write-ins or not; there has been a movement, against his will, to write-in Bernie Sanders for President, which has reached high single digits in other polls. Hillary may still break 60%, of course, but I'm a little inclined to doubt it. Combined Democratic candidates will probably improve from 2012, on the other hand.