The best populist leaders are those who manage to appeal to stirring themes of nationalism and fears of persecution without doing it so explicitly that their tricks are revealed. A good populist instils just the right amount of national righteousness without revealing the ugliness that lies at its heart. Theresa May’s “citizens of nowhere” soundbite had enough nativism without going all the way out into the territory of xenophobia. Michael Gove’s singling out of identity politics was a dependable trope that sent out the right signals about how minorities seek exceptional treatment. By this measure Donald Trump, the most successful contemporary populist, lacks the finesse, the flair for euphemism, the gentle breath on the dog-whistle that is required to galvanise a wide array of people. His foreign policy tweet last week about South Africa is a study in both how he is moving from populism to becoming an extremist, and how his pronouncements need to be analysed exclusively for their intent rather than their content.

With the conviction of both his ex-lawyer, Michael Cohen, and former campaign chairman, Paul Manafort, Trump reached for his most crude cudgel – playing on white nativist angst. While watching Fox News, he tweeted that he had asked his secretary of state, Mike Pompeo, “to closely study the South Africa land and farm seizures and expropriations and the large scale killing of farmers”. Then he quoted the headline from the Tucker Carlson show that had alerted him to this injustice: “South African government is now seizing land from white farmers”.

It’s not actually a dog-whistle if everyone can hear it: it’s a clarion call. He has dispensed with (or is not smart or patient enough to continue) maintaining the necessary cover for his signalling. It is no longer about the flag, or the anthem, or patriotism: it is about appealing to the most extreme and fanciful of fears among his voters about white genocide and reverse racism. Not that Trump necessarily cares deeply about white supremacy – it’s possible he didn’t even know that it is a cornerstone of white nationalist ideology to claim that South African farms are being expropriated from white farmers – but he thought it sounded like the sort of thing that his voters would be into. If it is useful to him, he will utilise it. If it is not, he will jettison it.

All this should make the job of those who wish to explain Trump’s actions much easier. He seeks to do two things: to distract attention from his gathering legal troubles, and to establish a connection with his base. He is indicating to them that, despite all they might be hearing about love children and affairs, he is still their man for entertaining their fantasies and grievances about race. By the time the South African government responded angrily to his “unfortunate and misinformed” tweet, Trump had moved on. He had successfully projected a white supremacist item of propaganda from the fringes fully into the mainstream, in the hope that this would make his supporters cleave to him even more closely. That is all. That is the headline and the main takeaway. One way that the media has tried to catch up with Trump’s runaway presidency is by fact checking. We know now, sometimes live during a speech he is giving, how many times Trump has lied. But it is not enough.

Whether it’s political correctness, identity politics or freedom of speech, rightwing politics today is conducted in code. And we need to get better at treating it as such, and deciphering it. So often, a threadbare fact is just dressed-up moral panic, and by the time the media has pored over all the details of it, the purpose of the claim has been achieved: to instil angst and fear, and to raise the profile of cynical politicians in the eyes of their existing and potential supporters.

Take Boris Johnson’s comments about the niqab face veil worn by some Muslim women, which he wrongly called the burqa (the full-length face and body veil). For days, the dominant conversation was about the “burqa” itself, rather than about what Johnson was obviously doing – making political hay out of an issue he cares in earnest so little about that he couldn’t even muster the motivation to get the nomenclature right, just to drive the point home.

We fell for it, as we continue to do with Trump. Writing this in the US, I have struggled – despite constant coverage of the Trump administration over the past two days (I counted a continuous five hours on CNN) – to find more than cursory attention paid by the media or politicians to examine or understand the racist nature of Trump’s tweets, even thought they could have been plucked from the white nationalist playbook if you look back in history. The New York Times editorial board did call his manoeuvre a “vile ploy”. But between outrage and earnest fact-checking, something is hiding in plain sight. In order to maintain his support and distract from his failures, Trump will gravitate to becoming the ambassador of white supremacists in the White House. The sooner that is universally acknowledged, the easier it will be to read his missives without getting distracted by their content. His transition from populism to extremism is under way.

• Nesrine Malik is a Guardian columnist