The latest LA Times/USC Nationwide Tracking poll has Donald Trump ahead of Hillary Clinton by six points! Maybe that poll is an outlier, a blip, mistaken in some way. And yet it’s not terribly out of step with other general election polls that have Trump ahead, even, or just a little behind. Sure, polls go up and down during a race, and maybe Trump’s lead will evaporate now that Clinton is back on the campaign trail, demonstrating that her collapse at the 9-11 event was not as serious as it seemed. But what if the lead doesn’t evaporate? What if...