This year has been dominated by the Russia-Ukraine war, recession, the China-US standoff, and the Hamas terrorist attack and Gaza war. Yet as earth-shattering as these conflicts and tragedies are, the next two years could aggravate them and surpass them all if the threat of a second Trump presidency comes to pass. At a moment that urgently needs a firefighter to stamp out the embers of conflict, Americans and the rest of the world may find an arsonist in the White House. It is not just the survival of American democracy that will be on the ballot in 2024 but stability and progress everywhere. A second Trump administration, in which he has brazenly vowed to be a dictator on day one, would be a disaster. Domestically, Trump’s “new independence” is no longer just an economic agenda. Gone is the 2016 talk of massive deregulation, privatisation of public services and big tax cuts. Instead, his policies are based on his personal prejudices and his desire for vengeance: deporting homeless people from urban areas, imposing death sentences on drug traffickers, legitimising “shoot and kill” even for shoplifters, repatriating the children of illegal immigrants whom he accuses of “poisoning the blood of our country”, purging free-thinking academics in educational institutions, and – what he says he will make his first act – clearing out what he calls the “vermin” and “traitors”, namely those government officials who would refuse to be yes men for his grotesque policies. When Trump engages in the conspiracy-theory politics of destroying “the deep state”, what he really means is that he will rule by presidential decree and where possible undermine independent federal institutions, thus destroying the checks and balances that have for two and a half centuries been at the heart of the American constitution. No longer would we be able to say that the rule of law and democracy prevails in America, that voting is free of interference or intimidation, or that power is properly accountable. He would kill for good any ideal of the “city on the hill”, and the liberal rules-based order with the US as the model for the world to emulate. Trump has already given us a preview of what awaits in this term, or what he calls his “final battle” for an “independent America”. This time around, Extreme-right thinktanks such as the Heritage Foundation are giving him detailed policy playbooks, like one titled Project 2025, which recommends radically reshaping government departments and consolidating power in the executive branch, that he could implement from day one. His international agenda would dramatically exacerbate the instability of an already unstable world. He has also boasted that he would end the war in Ukraine in 24 hours, no doubt by conceding to Vladimir Putin, and so even in the run-up to the presidential election, there is no incentive for Russia to come to the negotiating table. Trump’s vision of “America First and Only” is a dark summons to an insular and isolationist America, and an “us versus them” world of zero-sum politics. He conceives of a world where nations compete – like he did as a property developer – to destroy competitors, and thus the US can only win when others lose. And because he has threatened to renege on the US commitment to Nato to treat an attack on one country as an attack on all – he wants Europe to pay the US for American weapons supplied to Ukraine – the European Council is already discussing, with its document Strategic Compass, what President Macron calls “strategic autonomy” from the US. Four more years of the man who thinks climate change is a hoax and wishes to drill and burn oil and gas anywhere would also threaten the point of no return for the climate crisis. Trump’s neo-mercantilist economic agenda would have even wider ramifications for America’s allies and adversaries alike. Within days of his coming to power, he would impose a 10% tariff to place “a ring around the collar” of the US economy. While trade was once seen as the route to higher living standards, Trump favours the opposite: trade restrictions as the key to protecting living standards. The automatic overnight tripling of import duties would be a tax on US consumers, but it would at the same time destroy trading relations with every single American ally while creating a global wider economic downturn in the process. The IMF estimates that a full fracturing of the global economy would wipe out 7% of global GDP. This return to mercantilism would benefit no one. Overall, he would accelerate the shift to a more protectionist and multipolar world, and with his plan to withdraw from the World Bank, the IMF and the World Health Organization, attempts at international cooperation would be blown apart. The US, which tended to act multilaterally in a unipolar era, would act unilaterally in a multipolar era. Trump has been upping the rhetoric of vengeance for some time. As he declared at a recent rally: “I am your warrior. I am your justice. And for those who have been wronged and betrayed, I am your retribution.” But his policies are based not just on vengeance, but on ignorance. It is crucial to understand that Trump cannot be defeated by narrowing the difference between him and his Democratic opponents. It would be a mistake for them to dilute or abandon progressive policies and indulge in protectionism, mercantilism and xenophobia. Recent elections in Europe, where the far right has made considerable gains, show that if moderates allow the election agenda to be captured by the far right’s anti-immigrant, anti-environmental and anti-internationalist rhetoric, the far right wins. The evidence is that those Americans most likely to switch to Trump are those who now see the US not as a land of opportunity but as an “us versus them” society – in which you can only succeed at others’ expense. There is a pessimism about the country’s future because, for many years, a low-growth America has not been delivering for working people. They want a fairer society, and meeting Trump halfway on his anti-globalisation agenda won’t defeat him, but an open dialogue with the American people that elevates the case for fairness, justice, and equality will. Gordon Brown was UK prime minister from 2007 to 2010