David Brooks asks an interesting question: After everything that has happened in the last four years, why is the balance between the parties nearly unchanged? We could very well end up looking at a map of the election that looks almost exactly like the last one, although perhaps with Wisconsin and New Hampshire switching teams.

Brooks argues that the country’s division can’t be explained by foreign, economic, or social policy issues, because the division has stayed the same even though the issues being discussed have changed. He writes that two factors do account for the division. First is partisanship, the tribal instinct to root for one’s own team, especially “in a closely fought contest.” Second is two visions of leadership: Republicans prefer a soulful leader and Democrats a cerebral one.

I am partial to the “culture war” explanation of our political divisions (although I hate the phrase), and I don’t think that the social issues cease to be the basic division in political life on those occasions when they are not discussed. It would not be too hard, I suspect, to construct an account of how the underlying values divide would lead to different views of leadership. (There must be some reason Republicans and Democrats have different ones, assuming Brooks is right to say that they do.)

And how much can partisanship explain? It looks to me as though Brooks has come close to saying that the country is evenly divided because it’s evenly divided.

One tentative suggestion: Maybe the country is evenly divided because the political parties are efficient and their bases politically sophisticated. In other words, both liberals and conservatives are too demanding to allow their parties to gain too high a margin, and too pragmatic to allow them to sink too low. If the GOP were getting 60 percent of the vote routinely, conservatives would want it to move right–achieving more of their goals at the price of eliminating some of the vote surplus. Liberals, meanwhile, would give up some of their demands to help the Democrats get more votes. This is a simple model, to be sure, but the basic story seems highly plausible to me.