Donald Trump has used tweets to insult women and ethnic groups, and to drive news cycles over everything from his late-night TV choices to his midday food options. But he escalated his feud this morning with House Speaker Paul Ryan in a profound way, with implications and ramifications that extend far beyond November. “Paul Ryan said that I inherited something very special, the Republican Party,” Trump wrote on Twitter. “Wrong, I didn't inherit it, I won it with millions of voters!” On a basic level, Trump is right. He stands now as the presumptive Republican presidential nominee because of millions...