The April 5 Republican primary in Wisconsin is looking less like a toss-up between Donald Trump and Sen. Ted Cruz and more like a probable win for Cruz. This would be a fairly grave problem for Trump in his effort to reach 1,237 delegates ahead of the convention. Further, a new Wisconsin poll from a well-respected outfit shows horrific favorability ratings for Trump in the state among all voters, mirroring his recent national downturn. If he can’t reach enough delegates ahead of the convention, and his support shows signs of erosion in the final contests—all while his overall favorability rating...