When Americans turn their attention more fully to the 2020 election, voters will be interested in candidate proposals about health insurance, student debt, and the like. But the way to a Democratic victory is more likely one that also promises an end to the awful feeling that now pervades much of the country. That sense of constant war against each other. That floating dread about how far this will go. Americans have endured more than two years of ugly stories from Washington; stories of corruption, of conflicts of interest, of payments to adult-film stars, of secret meetings with Russians, of...