Like many of my fellow liberals, I would love to live in a country where Americans had never elected Mr. Trump — let alone sided with him by the millions in his claims that he won an election he lost, and that he did nothing wrong afterward. But nobody lives in that America. For all the power the institution has arrogated, the Supreme Court cannot bring that fantasy into being. To bar Mr. Trump from the ballot now would be the wrong way to show him to the exits of the political system, after all these years of strife.