“Guilty”, screamed the one-word headline in the New York Times last week, dripping with undisguised glee. Howls of contempt descended on Donald Trump as he slunk from his Manhattan courtroom to cries of “felon”. He now awaits sentence and three more criminal trials, two of them over his response to his 2020 election defeat. Ecstasy is a dangerous substance in politics. Trump’s enemies should be careful what they wish for. Within 24 hours of his leaving court, $39m reportedly poured into his campaign coffers. Though some Republicans seemed hesitant, an Ipsos poll for Reuters showed voting intention tilting in his favour. As with his victory in 2016, the more the political establishment damns him, the more those outside its reach are drawn to him. To many people in the US and around the world, the prospect of Trump’s return is the reduction to absurdity of the populist surge experienced by many western democracies. His still narrow lead in several polls has been enough to scare nervous Republicans to back him. To the House speaker, Mike Johnson, his New York conviction was “a shameful day in American history … a purely political exercise.” The same was true of the rightwing media. Rupert Murdoch’s New York Post replied to the Times’s “Guilty” headline with another single word, “Injustice”. To many jurists, the fact that Trump’s prosecutor, Alvin Bragg, was an elected Democrat who reportedly vowed to “get Trump” did indeed give the trial a political spin. This gives the former president a decent chance of victory on appeal next year. If that followed a “stolen” Biden win, there would be grounds for alarm. As Trump said at the weekend of his possible house arrest: “I am not sure the public would stand for it … There’s a breaking point.” The US Capitol attack on 6 January 2021 showed what that meant. As for Trump’s next trials, never was “the law’s delay” so clearly justice denied. The US judicial offices are highly politicised. It was Trump’s packing of the supreme court when in office that has helped stall any progress against him at the federal level. It has left him to dismiss local state prosecutors as political enemies. This in turn has added to his appeal among the “left-behind Americans” of populist folklore, those ignored by what he calls “the swamp”, the liberal elites of the nation’s east and west coasts. This gulf between “insiders and outsiders”, cities and provinces, cannot be ignored. It is evident in all western democracies. It underlay the Brexit referendum in Britain and is seen in support for Trump from Reform’s Nigel Farage and from Boris Johnson, who called his trial a “machine-gun, mob-style hit job”. Populists clearly stick together, however outrageous the cause. This means that for those who view another Trump presidency as a disaster, handling the next six months needs caution rather than cheering. Trump’s appeal to his supporters lies not in his affection for them but in the hatred he expresses for his enemies. It is why his support has been rising among non-graduates, the poor, African Americans and even Latinos. Joe Biden’s strength lies rather with the better educated and the better off. Old divisions between Republican and Democrat are meaningless in the age of populism. The answer cannot be to reason with Trumpism, which is more a stance than a programme. The television debate with Biden will be mere gladiatorial theatre. The strategy can only be to lower the temperature, to minimise publicity for Trump’s vapid accusations and bolster the virtues of Biden’s presidency and his increasingly uncertain leadership. Elections to the White House reflect the constitution’s balance of sovereignty between Washington and the states. They are when the states matter, in particular the dozen or so swing states that regularly change sides, where the contest is won or lost. As for the outside world, it normally cares about who becomes the US president. This time it cares about who does not. Simon Jenkins is a Guardian columnist