Iblame the father. Frederick Trump raised his children, one in particular, to believe that the world was divided into winners and losers and that there was no greater crime than to fall into the latter category. In 2020, Donald Trump was ready to bring down the American republic rather than admit before the shade of his dead father that he had lost a presidential election. Scholars speak of “losers’ consent” as an essential prerequisite of a democratic system: without it, there can be no peaceful transfer of power. For two and a half centuries, that model held in the US. But in 2020 it ran into a man who would rather destroy his country than wear the scarlet letter L on his forehead. The result is the indictment against Trump that arrived this week, the third – with one more expected – and easily the most serious. Across 45 pages, Trump is charged with plotting to overturn a democratic election – to thwart the will of the voters who had rejected him at the ballot box and thereby remain in power. The weary assumption is that, like the two previous indictments, this will not much damage Trump’s prospects in the 2024 election and might even boost them: a major national poll this week found him crushing all his Republican rivals for the party’s presidential nomination and dead even in the presumed match-up against Joe Biden. Even so, this case, whose court date will be set on 28 August, could scarcely be more significant. It will be the first great trial of the post-truth age. None of this should come as a surprise. Trump never hid who he was or what he intended. In 2016, he refused to say whether he would accept the outcome of the election he fought against Hillary Clinton: “I’ll keep you in suspense,” he said, and he was similarly coy four years later. Nor did he conceal his belief that his seat in the Oval Office put him above the law. Referring to the second article of the US constitution, he told an audience of teenagers in 2019, “I have an Article II, where I have the right to do whatever I want as president.” As for the impunity granted to him by his supporters, who give him more cash every time another felony charge lands, that too was foretold – by Trump himself. Back in January 2016, he predicted that he could stand on Fifth Avenue and “shoot somebody” and he would not lose any voters. So far, murder has not appeared on any Trump charge sheet, but the prescience of the remark still stands. More subtly, Trump revealed, and reveals, much of himself in the attacks he makes on others. He is currently insistent that he is the victim of Biden’s “weaponised” Department of Justice, suggesting that the independent federal prosecutors who drew up this week’s indictment were, in fact, mere partisan hacks doing the bidding of the president. And yet it is not Biden but Trump himself who has signalled that, if returned to the White House, he would end the independence of the criminal justice system, as part of a takeover of swathes of the administrative state, concentrating colossal power in his own hands. “What we’re trying to do is identify the pockets of independence and seize them,” one senior Trump lieutenant told the New York Times. It is Trump, not Biden, who envisages using the justice department as a hit squad against his enemies: he has promised, if re-elected, to order a criminal investigation into the current president. Again, no surprise: remember the way Trump led the 2016 crowds in anti-Clinton chants of “lock her up”. But just because we can’t claim to be surprised does not mean we shouldn’t be shocked. Several crucial principles are at stake in this case. One is that every vote must count: the victims of Trump’s conspiracy were the tens of millions of Americans who voted for Biden, whose ballots would have been cast aside had the ex-president prevailed. Another is that nobody is above the law. While Trump claims to be the victim of political persecution, the truth is that it would have been an intensely political decision not to pursue him, especially when more than 1,000 of his devotees have been charged for storming the Capitol on 6 January 2021. If they can be prosecuted for seeking to overturn the 2020 election, why can’t he? But perhaps the central principle at stake here is that there is such a thing as the truth. Trump has challenged that notion from the very start. Not just by lying – he’s not the first politician to do that – but by seeking to shake public faith in the very idea that truth is even possible. The former president spread specific lies claiming decisive electoral fraud in key states – as the indictment memorably puts it, “These claims were false, and the defendant knew that they were false” – in order to construct the big lie of a stolen election. He built an alternative reality on that lie that persists to this day – a reality made up, incidentally, of the kind of “alternative facts” to which we were introduced within hours of his taking office. That episode related to the seemingly trivial matter of the size of his inauguration crowd. But it established Trump’s post-truth position: that there are no commonly accepted facts – not even those you can see with your own eyes – only claim and counter-claim. That’s why one of Trump’s go-to lines has long been “Nobody really knows”. (“Nobody really knows” if climate change is real was a 2016 classic of the form.) In a blizzard of competing claims, the blinded citizen can either retreat, confused, or else be guided by the leader who kindly tells them what is true and what is not. That was the Putin manoeuvre – his power rests on it – and Trump has made it his own. Not for nothing is his personal social media platform called Truth. Now, though, Trump’s brand of post-truth is set to face its most severe challenge. As the Economist notes this week, “a courtroom is a place where reality counts … In court, truth means something”. Up until now, Trump has succeeded in persuading half the country that they cannot trust awkward, discomforting facts, including those uncovered by federal investigators, because all such people – FBI agents, judges – are tools of the deep state. Every morsel of evidence can be dismissed as the handiwork of the “globalists and communists” who constitute America’s “corrupt ruling class”. The tactic has been remarkably effective. The acid of Trumpian post-truth has corroded large parts of the US system already, breaking public trust in elections, the media and much else. Will the courtroom that hears the United States of America v Donald J Trump be able to shut it out and remain free of its sulphuric touch? On the answer, much more than the fate of one poisonous man – shaped by a poisonous father – depends. Jonathan Freedland is a Guardian columnist