American politics is a wonder for the world to behold. Our free speech traditions produce all kinds of interesting folderol, over the top in its theatrics and yet usually deeply meaningful to those participating in it. It was on display Monday, in front of the United States Supreme Court building, appearing seemingly by magic moments after President Donald Trump announced he’d chosen D.C. Appellate Judge Brett Kavanaugh to replace retiring Associate Justice Anthony Kennedy. The right was there. And the left, each itching to get their point across. They had signs, including some urging opposition to nominees not picked, pre-printed...