WASHINGTON (AFP) - From Mr Donald Trump to Mr Boris Johnson, the group of world leaders with an anti-system stance bordering on populism grows ever more powerful, crashing over global diplomacy and threatening multilateralism and international cooperation.
For many observers, the "populist wave" sweeping democratic countries claimed its first victory in June 2016 with the passing of the Brexit referendum, months before the election of a billionaire Republican as president of the United States.
Whether the term "populist" applies to conservative politician and Brexit champion Mr Johnson is a question for academics and future historians.
What is certain is that his appointment on Wednesday (July 24) as Britain's new prime minister, hard on the heels of the rise of far-right leaders such as Mr Jair Bolsonaro in Brazil and Mr Matteo Salvini in Italy, was welcomed by Mr Trump.
"When you look at the G-20 leaders, you see a lot of people now - almost half of the leaders - that generally speaking are friendly-oriented towards Trump as an American leader," said Dr Ian Bremmer, president of consultancy the Eurasia Group.
Mr Bremmer noted that many leaders propelled by the populist wave have come to power in Mr Trump's wake, pointing to Britain, Brazil, Italy and Australia, where Mr Scott Morrison is prime minister.
But he added that many had been in power much longer, including Indian Prime Minister Narendra Modi, Argentinian President Mauricio Macri and Turkey's Mr Recep Tayyip Erodgan, as well as leaders from more authoritarian countries, such as Russia's Mr Vladimir Putin and Saudi Crown Prince Mohammed bin Salman.
"I don't think (Boris) Johnson will be very comfortable in that company," said Dr Thomas Wright, the Brookings Institution director of the Centre on the United States and Europe.
"We see these leaders getting together and making some sort of illiberal pack... He is more moderate than they are."
While Mr Johnson is in the hard-line camp on Brexit, Dr Wright explained, he is more moderate on issues such as climate change and relations with Iran.
The journalist-turned-politician is "basically in favour of multilateralism", Dr Wright said, and risks finding himself at odds with the American president, who is supposedly his main ally.
The group of populist or populist-adjacent leaders may have different personalities and backgrounds, but they have a long list of similarities, too.
"They all share a populist style and are clearly part of the same broader political phenomenon," said Mr Luigi Scazzieri, a research fellow at the Centre for European Reform in London.
"Voters in the US, UK and Italy are embracing a brand of politics characterised by anti-immigration sentiment, the embrace of more or less explicit nationalist language, the rejection of traditional elites such as technocrats and experts," he said.
The movement is rooted in the rise of inequality, coupled with a growing sense of being undervalued, that has spread from the working class to the middle class.
"These men - Bolsonaro, Salvini, Trump, Boris Johnson - are really creatures of social media," said Dr Bremmer, noting that they have done "fantastically well" at using the online platforms.
"When you link those reasons together, you understand structurally why we're getting so much more populism in so many more countries," he said, adding that the "populist wave" is far from being widespread.
The emergence of the new far-right players has had a "profound impact on global affairs", noted Mr Scazzieri.
"Populist leaders also disparage international institutions as undermining national interests and sovereignty."
Mr Trump's "America First" formulation appears to have been applied in every country's populist language: "Brazil first", "Italy first" and so on.
The first victim has been the doctrine of multilateralism, and all its achievements since 1945, which Mr Trump and many of his international counterparts have targeted.
From the Paris climate agreement to the Iran nuclear deal, the United Nations to the European Union, the laws and institutions that have regulated the international order have all come under attack.
It is difficult, however, to talk about a "coalition" of "nationalist", "populist" or "anti-system" leaders: They make up a disparate group but are neither uniform nor unified.
For instance, after the spring European Parliament elections, it proved difficult to form a joint parliamentary group as questions about the economy or Russian relations divided the right.
"They all have different flags, they all have different national interests," said Dr Bremmer.
"It's easy for them to oppose globalism and existing international structures and free trade, but that doesn't make them agree on something. It makes them support more nationalist borders, more tariffs," he added.
"Populists' zero-sum mentality... leads to a less cooperative and more unstable international system," said Mr Scazzieri.