Sadiq Khan has linked Susan Hall, his Conservative challenger for the London mayoralty, with Donald Trump, saying a win for her could start a string of victories in 2024 for the extreme, populist right. Khan predicted this wave of hard-right populism could include Suella Braverman replacing Rishi Sunak as Tory leader. “This year will be a year of decision – there is every chance we could see Donald Trump in the White House, Suella Braverman in No 10, and Susan Hall in London’s City Hall,” the Labour mayor said, ratcheting up his rhetoric against an opponent who has backed Trump and liked tweets praising Enoch Powell. While polling shows Khan is well clear of Hall in the buildup to May’s vote, his team say the government’s decision to change the electoral system used for the mayoral vote – from supplementary to first past the post – could grant Hall a narrow win. Another complicating factor is the introduction of mandatory photo ID for voting. New polling commissioned by the mayor’s office showed that while 74% of Londoners are aware of the rules, this falls to 53% for younger voters and is also lower among some minority ethnic groups. Khan said the Conservatives had changed the voting system in “a deliberate effort to depress turnout [which] could open the door to a hard-right victory”. He directly likened Hall to Trump, the expected Republican candidate in November’s US presidential election, and Geert Wilders, whose far-right, anti-Islam Party for Freedom won the most seats in the Dutch parliament in November. “The mayoral election will likely be the first test of whether the extreme right can be held back,” Khan said. “Following Geert Wilders’ victory on our doorstep we know the far right are a real threat in European elections, and the prospects of another Donald Trump presidency could be even worse than his disastrous first term.” He added: “Here in London, one of the most diverse cities in the world, my Tory opponent in the mayoral election in May is someone who has repeatedly promoted divisive and racist content on social media, while attacking women and the Black community.” Previous research by the campaign group Hope Not Hate into the social media history of Hall, a London assembly member who has been a strong backer of Trump and of Liz Truss, showed she had liked tweets praising Enoch Powell, who became a byword for racism in UK politics after his “rivers of blood” speech in 1968 about immigration. At the time a spokesperson for Hall said she regularly engaged with people on Twitter, now known as X, “without endorsing their views and wholly condemns any racism or Islamophobia on the platform”. Hall also retweeted a message from the far-right activist Katie Hopkins that called Khan “the nipple height mayor of Londonistan”, adding: “Thank you Katie!” Londonistan is a common term of Islamophobic abuse, often used by the far right, to claim London has been taken over by Muslims. On the changes to the voting system, Khan said the Conservative government had echoed moves by other rightwing governments in “moving the goalposts to maximise their chances of winning – making it as hard as possible for potential progressives to vote and win”. Previous mayoral elections were held under the supplementary vote system, where voters could express a first and second choice, with their vote moving to the latter if their initial choice was knocked out. This often meant many Liberal Democrat and Green votes were transferred to Labour, but the move to first past the post means a split vote on the left could result in Hall becoming mayor with a relatively small minority of support. A spokesperson for Hall said: “Susan won’t take lectures on misogyny from Sadiq Khan, nor will Londoners be fooled by these desperate smear tactics after eight years of failure under his mayoralty. Londoners deserve so much better in 2024, with less crime and an end to his unfair Ulez expansion, and Susan is determined to deliver it.”