I lived in Wisconsin for my first 38 years, trust me, it’s a heartbreaker when it comes to Republican presidential politics, and it’s often misread. (see GHW Bush’s decision to visit the state 4x in the last 4 days of the 1992 campaign, because Mary Matalin thought it was close...lost by 5 pts.)
But, the narrower Hillary’s victory there, the better Ron Johnson’s chances. The total nightmare scenario is Hillary with an effective Democratic Senate majority (50 seats with Kaine as tie breaker.) She will have at least 2 and maybe as many as 4 SCOTUS nominations in a first term. That will hurt, real bad.