There are many ways to parse political divisions in contemporary America. There’s left vs. right, Democrat vs. Republican, liberal vs. conservative, pro-lifers vs. pro-choicers, free-traders vs. protectionists and red staters vs. blue staters, to name just a few. They’re part of the shorthand many of us use to signal to others, at least in a general way, where we stand on the issues of the day, and position ourselves along a political spectrum that stretches from far left to far right. But they’re often crude approximations prone to blur or break down under closer scrutiny and over time. And that’s...