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...