The president has been understandably confident in his supporters. They appreciate his efforts, admire his accomplishments (Justice Neil Gorsuch, ISIS’ setbacks), claim bragging rights for possibly related occurrences (the stock market’s rise), and feel sympathy for him as an outsider up against the swamp. They see his roughness as evidence of his authenticity, so he doesn’t freak them out every day. In this they are like Sarah Palin’s supporters, who saw her lack of intellectual polish as proof of sincerity. At her height, in 2008, she had almost the entire Republican Party behind her, and was pushed forward most forcefully...