Mayoral elections can seem set apart from the main drag of politics. People vote for individuals and their records, it’s not outlandish to stand as an independent, and even candidates within a party can float above it. It would be unusual, for example, to think “I can’t stand Rishi Sunak” (wait! That’s not the unusual bit) “therefore I won’t vote for Andy Street”. But even though they stand alone, paradoxically, you can see a huge amount about the bigger picture, globally as well as nationally, from these purportedly local ballots. Sadiq Khan has pretty unusual international name recognition for a city mayor, and the reason – no offence to him, his Hopper bus fares are good too – is that he has been the focus of racist and Islamophobic outbursts ever since Donald Trump called him a “stone cold loser” when the then-US president visited London in 2019. This has been interesting for two reasons. The first is the sheer contagion of anti-Muslim statements in mainstream politics and media, as well as attacks on Khan that are blatantly untrue and unfair, but slip in on the tide of normalised Islamophobia. You can trace a direct line from Trump’s outbursts to those of Lee Anderson, who was accused of racism this year, when he said “Islamists” had got control of Khan, who had “given our capital city away to his mates”. What started as an insinuation, that Muslims didn’t belong in public office, became an open statement through a process of transatlantic reiteration. In the layer below that, among those who facilitate what one might term “diet racism” – Fox News, GB News, sections of the Conservative party – it is now routine to describe London as a no-go area for Jewish people. This was a direct line of questioning to David Cameron by a Fox News anchor in April. The narrative is complicated by the fact that, in any single political speech or media encounter, there will be elisions and things left unsaid (except by Anderson, who leaves nothing unsaid). So Suella Braverman might describe pro-Gaza demonstrations as “hate marches”, but stop short of linking the hate to Khan; James Cleverly will take up the baton, and claim that the mayor talks “more about Gaza than black kids getting murdered in south-east London”, but stop short of drilling into those murders. That’s left to Susan Hall, the Conservative candidate for London mayor, who wrote that London was “under siege”, with “criminals ruling the streets”; these allegations were then given some statistical ballast by the Daily Mail, which claimed that gun crime had soared by 2,500% in London under Khan in a single year. That ballast was wrong, unfortunately, and corrected, but not before it had been repeated by the Tottenham Conservative Association, whence it found its way into the Telegraph. Through this perfectly visible but generally deniable exchange of tropes, exaggerations and untruths, where the loudhailer was thrown to the mavericks (Hall and Anderson) to get the most egregious lines out, a picture was constructed, internationally, of Khan as a mayor who’d turned our once great capital into Mad Max with extra antisemitism. And it has become routine in much more mainstream, putatively politically neutral outlets, like the Evening Standard, to perceive Khan as that “stone cold loser”, as if they’ve got Trump’s voice rattling in their heads, droning over the reality they can see in front of them. Last week, they described Hall as “closing the gap” when she briefly hit 27% in the polls to Khan’s 46% (at the time of writing, he is on 47%, she’s on 25%. So yes, even though that gap is tiny, you should still mind it). Compare all this to Andy Burnham, Manchester’s mayor. He also has pro-Palestinian marches on the streets, he’s also called for a ceasefire; he also has a great policy on buses; he also has a housebuilding plan roughly in line with Khan’s (1,000 new homes in every borough by 2028, London’s been promised 40,000 overall by 2030). They’re very similar, politically, and always have been. Yet Khan has been under sustained and accelerating racist attack since he took office, and Burnham hasn’t – and Burnham’s numbers are better, by a mile: 59% of Manchester residents have a favourable view of him, 15% unfavourable. Sadiq Khan is on 38% favourable, 40% unfavourable. This doesn’t map neatly on to voting intention, but it does tell us something about how information percolates to people who, in an ideal world, would be thinking about something other than regional mayoral elections. Messages don’t arrive clean and complete, neatly labelled with where they came from and which bits are true. Rather, they arrive as hints and vibes; huge statements like “he’s given our capital city away to his mates” might be taken with a pinch of salt, but leave a trace of half-remembered, entirely fictitious corruption. This is asymmetric polarisation in action: the right has been radicalised in its Islamophobia, and there has been no – or, OK, not enough – radicalisation in the fight against it. Khan said recently, in an interview with Mehdi Hasan: “In real time, I was calling out labour politicians and practices of the Labour party that were antisemitic... I would have hoped in the Conservative party, there would be Conservative politicians calling out what is clearly Islamophobic, anti-Muslim hatred.…” He added: “Who called it out? To this day... Rishi Sunak the prime minister hasn’t said what Lee Anderson said about me was islamophobic and/or racist.” Most people outside the Tory party have no trouble saying that. Why not the PM? Zoe Williams is a Guardian columnist