As mayors, they were strikingly similar. “They have in common this curiosity of having been directly elected mayors of very large global cities. That is a small club — in fact, there’s really only two members of it in the Anglosphere. … As mayor, they broadly came from the same ideological standpoint,” Tony Travers, an expert on municipal politics at the London School of Economics, says. They were both pro-business and pro-development, cut with dashes of environmentalism and social liberalism. Both stood on conservative tickets in famously liberal cities, and won.

“I should say how much every current mayor — and there’s a lot of mayors here today — owes to you, for what you’ve done, the leadership you’ve shown,” Johnson said. He praised Bloomberg’s ban on smoking in certain public places in New York; Bloomberg, in turn, said Johnson had done a “great job” with traffic policies in London. Toward the end of the discussion, the moderator, Walter Isaacson, asked both men about the widespread suggestions that they would run for higher office. When Bloomberg said he wasn’t planning on launching a presidential bid — because, he said, he wouldn’t win — Johnson mimed an incredulous expression, and mouthed, “Why not?” He tried to rally the audience: “Who thinks Mike could win?” A cry of support was not forthcoming. “They do,” Johnson reassured Bloomberg, of the audience. “Come on!”

In October 2015, Boris Johnson, then the mayor of London, and Mike Bloomberg, his former New York City counterpart, sat onstage at a conference in London and sang each other’s praises.

Both Bloomberg and Johnson did subsequently run for national office, at times when the center of political gravity in their respective countries had shifted toward “left-behind” regions far — culturally, economically, and sometimes, geographically — from the big cities they once led. While Johnson was able to shift his politics to accommodate that, Bloomberg was not. Johnson played a large part in the successful Brexit campaign of 2016 (I worked on the opposite campaign to Johnson’s); subsequently he became prime minister, and held onto power with a thumping election win last year. Bloomberg’s bid for the presidency, by contrast, is now over, following a poor Super Tuesday performance in which his sole victory came in American Samoa, despite his titanic advertising spending across the political map.

There are clear differences between the current politics of the U.S. and the U.K., the seismic realignments caused by Brexit chief among them. And, even as mayors, there were profound differences between Bloomberg and Johnson — not least in political style. “Johnson is a far more experienced speaker and television performer, and would not have made the mess Bloomberg made of the recent debate,” Andrew Gimson, Johnson’s biographer, says. And while Bloomberg built a business empire, Johnson once quit a management consultancy job after a week, because, he said, “I could not look at an overhead projection of a growth profit matrix and stay conscious.” More recently, Johnson allegedly said, in response to private sector concerns about Brexit, “fuck business.”

But where Johnson has been remarkably successful in shedding his metropolitan image — in part because of his willingness to indulge nativism — Bloomberg did not manage a comparable transformation.

The 2015 conference was at least the fourth occasion on which Johnson, as mayor, encouraged Bloomberg to run for president. He once called Bloomberg “the dean of our profession.” In a hand-scrawled note sent in 2015, Johnson praised Bloomberg’s “energy, dynamism, technological optimism, and can-do spirit,” adding that all he wanted to do was “take a fraction of that mental zap, bottle it, and uncork it somewhere in London.” On occasion, Bloomberg returned such compliments.

When Johnson was first elected mayor of London, in 2008, Bloomberg was one of the first politicians to call and congratulate him. He traveled to London within a week of Johnson being sworn in. Ahead of time, sources told The Telegraph, a British newspaper for which Johnson used to work as a journalist, that the visit would “play a key role in defining the Johnson administration” — both in policy terms and because Johnson wanted to emulate Bloomberg’s successes representing a conservative party in a liberal city.

After an early period of chaos, Johnson embraced a similar managerial style to that of Bloomberg, delegating many municipal functions to deputies, though perhaps for different reasons to Bloomberg’s. “I think in Bloomberg’s case, that would have been because as a businessperson, you need to be able to choose good people and delegate,” Travers says. Johnson, by contrast, has never seemed as interested in the nuts and bolts of governing. “Boris is not a technocrat,” Travers says. “He’s a political politician and nothing much more.”

Still, their respective tenures saw policy similarities, some of which initiated with Bloomberg, who took office six and a half years prior to Johnson. Some, but not all: Johnson aggressively championed the “Boris bikes” cycle-here scheme (he launched it and became synonymous with it, even though his predecessor initially planned it); years later, Bloomberg launched a similar initiative in New York. Through the years, the mayors spoke of having influenced each other on other projects, including around volunteering and urban green space.

Both mayors harbored obsessions with development — consequences be damned. On Bloomberg’s watch, roughly 40 percent of New York was rezoned; among other things, he oversaw the rapid gentrification of previously industrial parts of Brooklyn, and a neighborhood regeneration plan in Willets Point, Queens, that endangered that area’s working-class car repair industry. Johnson, for his part, erected controversial public artworks, and sunk more than $50 million of public money into a “garden bridge” over the Thames that never got built.

Like Bloomberg, Johnson endorsed stop-and-frisk policies as mayor. (He oversaw a slight expansion of London’s police force despite a sharp national decline in police numbers.) More broadly, both men left office with reputations — in progressive circles, at least — for favoring big business and the rich over their cities’ neediest residents. New York and London were reshaped, of course, by broader forces of globalized capital, and not merely by Bloomberg and Johnson. But as Travers puts it, the mayors “just embraced them.”

It’s no accident that Bloomberg and Johnson’s respective successors, Bill de Blasio and Sadiq Khan, ran on platforms highlighting those who were being left behind by inequality. (Though Khan and Bloomberg are friends, and before Bloomberg dropped out, Khan indicated that he’d like to see Bloomberg take on Trump in November.)

In 2015, as Johnson neared the end of his tenure as London mayor, outlandish rumors started to circulate in the press that Bloomberg might try and run to replace him, on the Conservative ticket. (Bloomberg is an honorary knight of the British Empire and has called London his “second home”; his significant financial investments in the U.K., party sources said, could have fast-tracked a bid for citizenship.)

In a Facebook post, Johnson wrote that there might be something in the rumors — and said that if they were true, he would approve. “There is only one way to graduate upwards from the position of Mayor of New York,” Johnson wrote, “and that is to become the leader of a city that has regained its status as the greatest on earth.”

Since then, Johnson has managed to graduate into a higher role. Why could Bloomberg not achieve a comparable feat? Critics of Johnson say he has always been a political chameleon with no true beliefs, willing to say different things for different audiences to gain and keep power; there’s no contradiction in Johnson being a relatively liberal mayor of London and then an illiberal prime minister, such critics say, because both positions are a facade. Bloomberg does not fit in the same category. “They are opposite ends of the spectrum politicians,” Sonia Purnell, another biographer of Johnson, says. “Bloomberg is quite dry, technocratic … managerial. Johnson can’t run a whelk stall — let alone a city and heaven forbid a country hit by multiple crises — but he has an astounding gift for self promotion.”

“My charm, if you will, is that I say what I believe — and do it. Unfortunately, some people don’t like that,” Bloomberg said last year, with his typical charm.

There are other aspects of Johnson’s recent transformation — including tapping into nativist, anti-immigrant sentiment among sections of voters — that weren’t available to Bloomberg. For starters, he was looking to run on the Democratic ticket. “It’s just not gonna happen on a national level for somebody like me starting where I am, unless I was willing to change all my views,” Bloomberg accurately forecast in 2019. And unlike Johnson, who has long played the part of a quintessential British eccentric, Bloomberg’s name is synonymous with his financial media empire and international philanthropy.

Still, a large part of Johnson’s success has come in winning over voters in the north of England who traditionally have supported left-wing parties. In the U.S., too, it’s not just the right that’s seen a backlash against the sort of neoliberal, urban-centric politics Johnson and Bloomberg practiced as mayors. Both wings of the Democratic Party are looking for a presidential candidate who can appeal to suburban and rural “heartland” voters who feel alienated from big-city capitalism, even if they disagree on how to do that. A big-city, overtly pro-business technocrat doesn’t fit the bill.

Where Johnson shed his political skin to match such sentiments, Bloomberg tried an alternative strategy — to spend whatever it took to win power, without fundamentally reinventing his image or platform (his conveniently timed apology for stop-and-frisk notwithstanding). As a candidate, Bloomberg repeatedly emphasized his mayoral record and the virtues of technocracy — not least in a coronavirus-themed ad dressed up as a faux presidential address to the nation.

It’s not clear if Bloomberg and Johnson still talk. (Bloomberg’s presidential campaign, before it folded, did not respond to a request for comment.) But Bloomberg certainly took a dim view of Johnson’s post-mayoral pivot — mostly due to Brexit, which Bloomberg once called “the stupidest thing any country has ever done.”

In an interview with Britain’s Sunday Times in 2018, Bloomberg was asked about Johnson, and shook his head. “When he was mayor we spent a lot of time together,” Bloomberg said. “I don’t know how he went so crazy.”