You remember the photo, taken in early August, of two men at an Ohio Trump rally whose matching T-shirts read, “I’d rather be a Russian than a Democrat.” (Now you can buy them online for $14.) It was a gibe that spoke to our moment. The Republican brand — as with presidential nominees John McCain and Mitt Romney — used to be pointedly anti-Russian; Romney called Moscow our chief global enemy. In the Trump era, though, you can be a Republican Russophile for whom Vladi­mir Putin is a defender of conservative values. American politics, it has become plain, is driven less by ideological commitments than by partisan identities — less by what we think than by what we are. Identity precedes ideology.