No sooner had the words “preserve, protect and defend” the constitution of the United States fallen from his lips than Donald Trump laid into it – the very system symbolised in the elegant buildings, time-honoured ceremonial and distinguished figures surrounding him.

I’ll give him full marks for chutzpah, at any rate. There, before the former presidents, former vice-presidents, Supreme Court justices, senators, congressmen and congresswomen, first ladies, spies, military chiefs and Washington bureaucrats, Donald Trump decided to condemn them all as failed. Not only failed, but revelling in their failures – celebrating their success in Washington while “forgotten” American workers and families suffered from sea to shining sea.

Politicians, Trump declared, had done nothing to prevent the “ravages” of foreign powers “stealing” Americans' jobs and hopes. They had defended other nations’ borders, and not those of their own homeland. He did not quite accuse President Carter, President Clinton, President GW Bush and President Obama of high treason – but he was not far off. They must have been cringing with embarrassment at Trump’s clumping around everything they stand for.

To “all Americans”, Trump declared, “You will never be forgotten again” – just as all those scoundrels who went before wilfully had, he implied.

Protests mar Trump inauguration ceremony

What’s wrong with all that? It is that this brand of populism, infused with strident nationalism and an unthinking protectionism, undermines faith in democracy itself.

Yes, people have always regarded politicians as “in it for themselves”, their reputation not far above that of journalists and estate agents. The old joke ran that a politician would beg people not to tell his mother that he’s a politician because she thinks he plays the piano in a brothel. Political corruption is nothing new, and the democratic process has also always succeeded in cleansing the system and renewing itself.

But this is different. It is rare to find a figure such as Trump going all out to not only take down individual figures, but the whole political class and, in fact, the whole political system. What else should people expect from “the swamp” but lies?

History provides ugly examples from the first half of the 20th century, when people lost faith in “politicians” and then slid into losing faith with the democratic process itself. Trump said nothing to defend the democratic process that put him in power, that led him to the stage on which he delivered his inauguration speech. He spoke just as he did on the campaign trail, as a demagogue, a would-be dictator, a man who wishes to replace democracy with populism – and they are not the same things.