If Jennifer Palmieri could turn back the clock, and make one change to Hillary Clinton’s campaign, what would it be? I can guess any number of answers when I put the question to the campaign’s communications director, but not the one she gives. “I would have spent more time and money,” she replies without hesitation, “in Texas, Arizona and Georgia.” Palmieri’s explanation makes perfect sense. She says they made the classic mistake of devoting their energy to the swing states of previous elections, such as Ohio, while overlooking historically safe Republican states now becoming winnable due to shifting demographics. It’s...