Don’t interrupt your enemy when he is making a mistake, said Napoleon. So what is President Trump playing at? The further Left the Democrats go, the more determinedly he drags the debate back to the Identitarian culture wars that disfigure modern American politics. When the Democrats are talking about whether men have the right to an abortion, why switch the argument back to whether second-generation Americans should go “back” to “their” countries?

One answer might be that, distasteful as they are, such statements are popular. The consensus of the pollsters is that Trump enjoyed a two- or three-point lift after his controversial remarks, though it is necessarily difficult to disentangle the effect of what he is saying from the general craziness of the other side.

Again and again, commentators have declared some remark of Trump’s to be political suicide, only for him to rise in the polls. The mocking of John McCain, the attacks on the family of a fallen serviceman, the lurid conspiracy theory about Ted Cruz’s father, the physical mockery of female opponents, all were supposed to sink him. All, instead, floated him higher.

Why? One of the more convincing takes on current politics comes from two professors at the University of North Carolina, Marc Hetherington and Jonathan Weiler. They have shown that, although we all like to imagine that our political views are based on reason and logic, they mostly reflect our basic intuitions. The most elemental divide of all is between the people that they call “fixed” and those they call “fluid.” The fixed people value order, certainty, hierarchy, stability, and respect. They fret about crime and see immigration as a problem to be managed rather than an opportunity to be grasped. The fluid people value innovation, curiosity, multiculturalism, and empathy. For them, the world is full of opportunities. Those of the fixed mindset see fluid people as dangerously naïve, while those of the fluid mindset see fixed people as bigoted. Sometimes, both are right.

Trump’s achievement has been to align the political parties almost exactly along the fixed-fluid axis, at least among white voters. Lots of things that used to define the Republicans but that are not integral to the fixed worldview have been downgraded or abandoned altogether. The party no longer stands as it used to for free trade, small government, or American global leadership. It has followed its leader to an altogether more protectionist, nativist, and isolationist stance. If, like me, you are an old-fashioned free-marketeer, you may be distressed by the rapidity with which the GOP junked its principles. Still, we limited-government types should be honest and accept that statist conservatism has always been popular. Fretting about the deficit, or about the excessive use of executive orders, is a minority pursuit.

Whether through deliberate strategy, or by fluke, or possibly in some idiot savant way, Trump understands that the fixed people outnumbered those who are fluid. To put it more precisely, voters in the middle incline more to the fixed than to the fluid perspective on key issues such as immigration, crime, and cultural identity. This is largely because, as Jonah Goldberg showed in his magisterial book Suicide of the West, liberal democracy is unnatural, in the sense that it runs up against our hunter-gatherer instincts and intuitions. Trump’s admirers applaud him because, on some deep genetic level, he is a tough tribal leader. He divides the world into us and them, hits the other side where it hurts, and takes no prisoners. Modern people are taught to worry about consistency but, on a genetic level, the fact of winning matters more to us than its purpose.

The same dynamic applies on the Left. Trump’s opponents are as likely as he is to think in terms of “us” and “them.” They, too, care more about approbation from within their tribe than about reasonableness. Hence their retreat into purer and purer, or depending on your point of view, weirder and weirder, policies, from mandatory transgender bathrooms to open borders. Hence their readiness to dismiss their opponents as "deplorables" rather than seeking to win them over. If you are looking for a five-word explanation for the 2016 presidential election, look at the cover of the loser’s book, What Happened by Hillary Rodham Clinton.

It is worth remembering that Trump won fewer votes than John McCain or Mitt Romney. But it didn’t matter, because the complacency, entitlement, and general haplessness of the other side was enough to put him in office.

Napoleon is also supposed to have said that the quality he looked for above all others in his generals was luck. In 2016, Trump was lucky in his opponents. Those opponents have responded to their defeat by retreating even further into partisanship and introversion. The president’s luck is holding.