The Trump campaign is really digging deep in the far-right archives for its rhetoric in the closing days of the 2024 presidential campaign.

The manifestly unfunny joke by one of his supporters at Madison Square Garden this week that Puerto Rico is a “floating island of garbage” could end up costing Trump the election. But the revival of old discourses of pseudoscientific racism by both Donald Trump and several supporters around him haven’t drawn as much scrutiny. Trump’s obsessive fixation on Kamala Harris’s race and intelligence, with the constant refrain that she is a “low-IQ individual,” has been going on for months.

The insult evokes the racist ideologies of the twentieth century that have recently become more popular in the right-wing manosphere. Their prominence in a modern presidential campaign marks a dangerous devolution in our national politics.

There are plenty of intellectually unimpressive individuals in our political landscape. Our current president is himself no Rhodes Scholar — not now, well into his senility, and not ever. But Trump and his allies aren’t interested in whether Joe Biden is smart. That’s because the far right has only one reason for ever bringing up the measurement of human intelligence at all: the opportunity to claim, falsely, that some racial groups, including black Americans, are genetically less intelligent than others. This is an idea that has been debunked again and again since its early days, but it persists — and has been enjoying a disturbing renaissance recently, thanks to Trump.

Trump used the “low IQ” epithet at his Madison Square Garden rally. But that wasn’t the first time. He often repeats it at his rallies, as well as in his recent interview with Joe Rogan, who lamented in 2018 that, due to the constraints of political correctness, “You can’t even discuss the fact that certain races have low IQ.”

At the Madison Square Garden rally, Tucker Carlson amplified this with a truly wacko twist. Imagining the aftermath of the election, in which he assumed that the Democrats would falsely declare victory, he said,

It’s going to be pretty hard to look at us and say, “You know what? Kamala Harris, she got eighty-five million votes because she’s so impressive as the first Samoan-Malaysian, low-IQ, former California prosecutor ever to be elected president.”

Talk about weird. For one thing, Harris isn’t Samoan or Malaysian. But here again, the right-wingers are dabbling in very old-school racism. Nineteenth-century racists were obsessed with trying to racially classify Polynesians and determine how close they were to whiteness. And “Malay” was an early category invented by German naturalist Johann Blumenbach of that same era, who has been called the founder of racial classifications. (While he didn’t actually believe that some races were inferior to others, his preoccupations with classification influenced many later supposedly science-obsessed racists.) Blumenbach thought Malaysians were somewhere in between Caucasians and Ethiopians and spent a lot of time trying to figure out how to classify them.

Carlson wasn’t just making a mistake here: he was signaling loudly to fellow scientific racists that Harris is part of an inferior group of people.

One thing that makes the “Harris has a low IQ” insult remarkable in its racism is that — with or without the “Samoan-Malaysian” eugenic fever dream — it wholly lacks that grain of truth that often gives Trump’s invective some real bite. It was funny when Trump called Jeb Bush “low-energy,” Marco Rubio “Little Marco,” and Biden “Sleepy Joe.” It was also funny when he said that Volodymyr Zelensky was a great salesman because whenever he visits the United States, he walks away with $60 billion.

Calling Harris a “low IQ person” isn’t like any of these comments, because there is no truth to it. Harris is an accomplished public servant who demolished Trump in the one debate he had the guts to participate in.

An individual politician’s personal smartness is an overrated thing. On the presidential campaign trail, Bernie Sanders used to downplay his own smarts as part of his “not me, us” approach to politics. But Trump’s insults to Harris aren’t really about her intelligence. The only reason the remark is memorable or has any potency is that it’s very racist and uses long-established idioms of racism.

Obviously, racism, by marking some groups as inferior, exposes real human beings to violence, discrimination, and genocide. When people draw comparisons between Trump and Adolf Hitler, they’re expressing fears about just what he might do with all this racism (and recently, describing his plans to deport all the migrants, Trump has seemingly embraced this Hitler bogeyman).

But while the human rights implications of Trump’s racism are real, what’s equally dangerous about it is how much it erodes social solidarity. That’s precisely what racism is supposed to do. Racism is divisive, and for Trump and his ilk, that’s the point. Dividing the working class — from the Democratic Party, but more importantly, from one another — has always been his entire political appeal, the reason he is so beloved by right-wing billionaires like Elon Musk and Peter Thiel, as well as by provincial elites who don’t want to pay taxes or deal with unions.

Racism also makes collective projects impossible: people who think some groups of people are inherently stupid or criminal don’t want to build a collective future with those inferior others. This renders impossible all the things that we need to do as a society: educate children and young adults, build great public transit and other infrastructure, house people, improve health care, preserve our natural environment, build renewable energy. Republicans don’t want to do any of that, so whether they share Trump’s racism or not, it suits them quite well.

For their part, Democrats love to condemn Trump’s racism, but they don’t challenge that same eugenicist logic when it comes to genocide committed by American allies like Israel: when it comes to the Middle East, not all lives matter. Nor do Democratic Party leaders see what’s at stake when Trump calls Harris a “low IQ individual”: he’s not just being an offensive jerk — though he plainly is doing that — he’s also contesting the vision of a society where everyone matters, and where everyone belongs.

If the Democratic leaders believed in that vision, they’d be able to make a compelling case for what such a society would look like, rather than simply recoiling in horror from Trump’s disgusting racist spectacles. Maybe then the election wouldn’t be so precariously close.