His spelling and grammar are disastrous, he contradicts himself, trails into incoherence, never sounds dignified or recognisably presidential – but none of it does him any harm. In fact, it seems to help

‘It’s all fake news, it’s phoney stuff – it didn’t happen … I think we have one of the great cabinets ever put together … Don’t be rude. Don’t be rude. Don’t. Be. Rude … I’m not going to give you a question. I’m not going to give you a question. You’re fake news.” In his first press conference, President-elect Trump was fiery, abrupt and off-the-cuff. He spoke less like a president than like a bad-tempered reality TV star with – in Lord of the Flies terms – a firm grip on the conch.

Public oratory has been at the centre of the American project from the time of its founders. The framers of the constitution gave themselves classical noms de plume in their correspondence, and consciously modelled their new nation on the Roman republic. Every presidency is punctuated with set-piece speeches, and its historical turning points have been marked by historic speeches. In Donald J Trump, though, we have a presidential communicator who is quite unlike the other ducks.

So what does this augur for the public face of his administration? How does his language work? On a purely linguistic level, three things seem striking.

1) Trump uses a pretty small working vocabulary. This doesn’t seem to be a conscious strategy, though it works as well as if it had been. Much was made during primary season of the way in which reading-level algorithms (unreliable though they are) found his speeches pitched at fourth-grade level, ie the comprehension of an average nine-year-old.

2) His syntax, spelling and punctuation are – in conventional terms – a catastrophe. In his tweets, he is prone to run-on sentences, shouty capitalisations, unpresidented misspellings and malapropisms, quote marks used for emphasis and verbless exclamations. In speaking, he is prone to anacoluthon – sentences whose grammar collapses – and reflexive repetition.

3) The workhorses of his rhetoric are charged but empty adjectives and adverbs. Things are “great”, “wonderful”, “amazing”, “the best”, or they’re “crooked”, “fake”, “unfair”, “failing”. He sprinkles intensifiers liberally: “a very, very, very amazing man, a great, great developer”.

Facebook Twitter Pinterest People mistrust smooth talkers, and Barack Obama’s showy articulacy didn’t always count in his favour. Photograph: UPI / Barcroft Images

All of those qualities, though they invite sneers, have something to be said for them as communicative strategies. Simple language reaches the widest possible audience and it tends (insert rueful joke here) to connote honesty. The plain style – short words, simple syntax and a folksy approach – has long been a winner for presidents. Remember George W Bush pretending to be a down-home Texan cowpoke? Remember Ronald Reagan playing “the Gipper”? Remember Bill Clinton playing the good ol’ boy? People mistrust smooth talkers, and Obama’s showy articulacy didn’t always count in his favour.

Simple (or absent) grammatical structures leave the audience with nothing so taxing as a train of thought: rather, a random collage of emotive terms, repeated for emphasis. You come away from a Trump speech with a feeling, not an argument.

Trump’s plain style is unvarying, though, and that’s a key part of his ethos, or how he projects himself to his public. Most of his predecessors were able to command a range of registers. The presidential – dignified, high-flown – was available to George W Bush even as he struggled with his syntax (a struggle that, as I’ve suggested with Trump, didn’t necessarily hurt him). It was abundant in Obama. And it underpinned even Reagan’s folksiness.

In fact, the ability to shift register mid-speech – to say something historic-sounding but then to humanise it with a confidential joke, a mention of “folks”, or a self-teasing personal anecdote – has been a basic presidential skill. Lincoln certainly had it. And even on the attack, Trump’s predecessors never sounded petulant. They worked to convey either grave seriousness, or a sense of command so absolute that contempt was expressed as amusement. Think of Obama’s deadly sally at John McCain – “I don’t believe that Senator McCain doesn’t care what’s going on in the lives of Americans; I just think he doesn’t know”; or Reagan smirking at Jimmy Carter, “There you go again …”

Facebook Twitter Pinterest George W Bush struggled with his syntax but even he could shift registers and sound dignified. Photograph: Mark Wilson/Getty Images

In Trump, there is a note of wounded vanity, and of spite – “Meryl Streep, one of the most over-rated actresses in Hollywood” – that you struggle to find in recent presidential history other than in Nixon’s private conversations. Trump simply doesn’t sound presidential, ever. He doesn’t have different registers for different occasions: he always sounds boastful, vengeful, bullying and naive.

To many of us, that looks like a failing. But to some, we might have to accept that it’s a selling point: he doesn’t sound like a normal president, and that’s why people like him. There’s only one Donald Trump. What you see is what you get. That can be seen as a sort of authenticity.

A related point: where Trump’s language differs most profoundly from that of any of his predecessors is in his ability flatly and unblushingly to contradict himself. I’m saying this not to rattle my pearls at how awful he is, but to marvel at how it works rhetorically.

Most politicians are good at being equivocal. They are“economical with the actualite”; they “misspeak”; in extremis, like Bill Clinton, they may quibble over “what the meaning of ‘is’ is”. But they do not like to say something that is unequivocally, checkably at odds with the truth of their behaviour or with their previous statements.

Winning words: the language that got Donald Trump elected Read more

This is because, as a rule, the most effectively damaging charge against a politician has been dishonesty – or its practical cousin, hypocrisy. The media can say you are wrong or even evil. But these attacks don’t nail you to the wall. They can be ascribed to ideological opposition or to differing interpretations of data. If you said X and you did Y, or you said X and they prove you knew Y was the case, you are sunk. You have damned yourself on your own terms.

This rule shows all signs of having been suspended for President-elect Trump. Yes, a lot of the time he’s vague. But when he does say things that are concrete, he says them directly: I never supported the Iraq war; Alicia Machado made a sex tape; I saw thousands of Muslims cheering 9/11; Hillary Clinton started the rumours about Obama’s birth certificate but Donald Trump “finished them”, and so on. Often those things can be proved to be untrue, or contradict something he previously said. Yet that seems to do him no harm at all.

I wonder at this as much, I imagine, as you do. My hunch is that we have an electorate so used to politicians being equivocal, and so enraged by it, that the bounce Trump gets from not sounding like that is much bigger than the demerit he incurs for being a clouds-of-smoke-billowing-from-his-pants liar. We’d rather have an open liar, in other words, than a conventional politician. Let’s see how that works out.

Sam Leith is the author of You Talkin’ To Me?: Rhetoric from Aristotle to Obama (Profile Books). To order a copy for £7.64 (RRP £8.99) go to bookshop.theguardian.com or call 0330 333 6846.