 The crowd there chanting, fight, fight, fight, the words that Donald Trump used on that Pennsylvania stage just moments after he was shot at the weekend. Well, his appearance, more or less, overshadowed the other news of the evening, the announcement that J.D. Vance, a relatively unknown 39-year-old senator from Ohio, is to be Mr. Trump's running mate and vice presidential candidate. Vance was once a Trump critic.