This one is weird. It has 11% undecided and 9% "would not vote". I guess the rest are "others".
Wisconsin might actually be one of the better states for third party candidates. They don't seem to like Clinton or Trump much.
In my 18 years in the state I never saw any third-party candidate other than Perot gain much traction, and he was more a protest vote than anything else.
Wisconsin is split down the middle between staunch conservatives and labor-progressive Democrats. The former really don't like Trump, while the latter will unify behind Clinton, despite Sanders having won the primary. Huge advantage to Clinton.