Donald Trump once joked that he could shoot someone on Fifth Avenue and not lose votes. That may be true—his approval ratings have inched up recently, tweetstorms and Stormy Daniels notwithstanding.
But can he be re-elected? He’s unlikely to face an opponent as unpopular and uninspiring as Hillary Clinton in 2020. His best hope may be John Kasich. The departing Ohio governor has made noises about challenging Mr. Trump in the primaries, but an independent bid would be better for the president.