A Democrat campaigning for the White House must feel like a soldier advancing through a mine field. At any moment, he or she is one step away from being blown out of the contest. And the poor wretch is surrounded by a ravenous mob of media hounds, each of whom is eager to set off the fatal charge. Gotcha! Still worse, almost all the media volleys are fired toward the port side. If a Republican or (so-called) “conservative” makes a gaffe, as they do almost daily, their “misspeak” is usually politely ignored. Or if it is simply too awful to...