“Things fall apart. The centre cannot hold.”

— William Butler Yeats

And so this is the presidential campaign of 2016.

If it were a movie, it would be pornography. If it were a sporting event, it would be a cockfight. If it were music, it would be the sound of cats on a hot blackboard.

In other words, it has not been the most high-minded affair.

But beyond the fact that it has been ugly and dispiriting, the campaign has also come to feel … ominous, like a portent of some dystopian future. You wonder if maybe the superficial nastiness of it isn’t truly superficial at all, but rather, evidence of a grim new reality: that we are a nation of 323 million people in 50 states who not only are not united, but don’t particularly want to be.

It is hard to escape a sense that at some level, we have disengaged from one another and that as a result, our politics has shrunken to its extremes, like two boxers who retreat to neutral corners to yell across the ring.

Two men in particular embody this. The first, of course, is Donald Trump, who has channeled angry misanthropy into political power. The reality show impresario has pulled the Republican Party far to the right, using as his prod the inchoate, done-wrong, want-my-country-back rage of those for whom change is always, by definition, threat.

The second man is Bernie Sanders, who has channeled the angry populism of the political left into a movement that is no slouch for power itself. The Vermont senator has yanked the Democratic field — i.e., Hillary Clinton — far to the left, forcing her to compete for the affections of angry, tired-of-being-dumped-on 99 percenters who see democracy being stolen by Big Money and like it not at all.

Don’t misunderstand the point. Sanders has given voice to concerns too often ignored by Republicans and paid lip service to by Democrats. So the argument here is not that there is equivalence between the extremes of left and right. No, the argument — the observation, really — is that they are both, well … extremes. And that, apparently, that’s all our national politics has left.

It is instructive to watch Clinton and Sanders bicker about which is the more ideologically pure. Until recently, that kind of quarrel was restricted to Republicans jousting over who was most “conservative” — by which they meant draconian — on issues like immigration and abortion. Now, apparently, Democrats, too, want their candidates to pledge allegiance to philosophical dogma.

It raises a question: Whither the center? And if there is no center, how does the nation’s business get done? As ungovernable as the country has been under Barack Obama, a center-left pragmatist the Republicans made out to be the reincarnation of Che Guevara, it can only be worse under a leader whose ideological purity is zealously policed and for whom compromise is apostasy.

One struggles to even imagine what the fall campaign will be like. Usually, candidates argue over who has the best ideas for solving a given set of problems. But in neutral corners America, there is not even consensus on what the problems are. Will we have Trump campaigning on Mexicans and Muslims, while Sanders rails about money and malfeasance? Will we be asked only to decide which makes us most angry and afraid?

If so, whither hope?

And here, Democrats will want it noted that they were not the first to abandon the center. Let the record so state. The GOP eschewed all claim to that ground long ago and even purged itself of members who dared wander too close.

Still, the question of who is to blame for a politics of extremism is less compelling than the question of what that politics portends. Two boxers yelling at one another from neutral corners makes for great theater.

But the fighting is done in the center of the ring.

Leonard Pitts is a columnist for The Miami Herald, 1 Herald Plaza, Miami, Fla., 33132. Readers may contact him via e-mail at lpitts@miamiherald.com.