In any primary, there are a thousand questions to ask, but the first one – yes, the primary one – must be this: What year is it? No, not just “is this a presidential year or a midterm election,†though that’s important too... But what year is it, historically? That is, is it most analogous to a year we’ve seen before, or is it unlike any prior election, so we shouldn’t bother to see if we can learn from parallels? It is often said that there is nothing new under the sun, that we’re always fighting the same war, that...