Contrast two leaders. Donald Trump’s approval ratings barely budged during his presidency, and his supporters dismissed every scandal as “fake news”. But when Boris Johnson turned out to have doubled as a party host during lockdown, his supporters fled: his net favourability rating went from +29 per cent in April 2020 to -52 per cent last week, according to pollsters YouGov.

Here, in microcosm, is the uniqueness of American polarisation. People often discuss polarisation as a global problem, but in fact, in most western European and even Latin American democracies, rival camps aren’t deeply entrenched or always entirely serious.

Western polarisation peaked between 2016 and 2018, with the victories of Brexit, Trump and Brazil’s Jair Bolsonaro, the violent clashes over Catalan independence, and the entry of the anti-system Five Star and nativist League into Italy’s government.