Key figures in Momentum – the pro-Corbyn activist group – have been called in to advise progressive organisations trying to reverse the rightward lurch of American politics under Donald Trump.
Two of Momentum’s founders have spent ten weeks across the Atlantic sharing the campaigning techniques credited with helping Labour to confound predictions by wiping out Theresa May’s majority at the general election.
Emma Rees and Adam Klug have been advising US activists pressing for free universal healthcare and the election of progressive state attorneys.
They hope some of their methods will lead to success for left-wing candidates in mid-term elections to Congress in November and ultimately to Mr Trump’s removal from office in 2020.
Momentum established transatlantic links when supporters of the radical Democrat Bernie Sanders came to Britain in 2016 to support Mr Corbyn in his second leadership contest and to help the Momentum campaign effort in last year’s general election.
In the US Ms Rees and Mr Klug worked with the National Nurses United union on incorporating Momentum’s “persuasive conversations” technique – where supporters are given campaign skills – to boost its drive for free healthcare.
The policy is now backed by 60 Democrats in Congress.
Ms Rees said the issue has “gone from the fringes of the Democratic Party, which shows how the ground is shifting”.
The pair have also advised the leaders of Real Justice, a group founded by a former Sanders adviser, which is pressing for a broader social mix of district attorneys.
It is experimenting with an American version of Momentum’s Unseat events in which large numbers of activists are dispatched to campaign for Labour in marginal Tory seats.
Ms Rees said: “It’s possible to learn from each other’s experiences and campaign techniques ... that sort of work is going to have an impact on the presidential election.
“The combination of big politics and big organising is clearly gaining traction and having an impact.”
They have also made contacts within the Leap movement in Canada, which is arguing for social change combined with dramatic moves to cut the use of fossil fuels.
Ms Rees also pointed to the success of unknown community activist Alexandria Ocasio-Cortez in defeating a long-established incumbent to gain the Democratic Party nomination to stand in New York for Congress.
Momentum has invited Ms Ocasio-Cortez to appear at the World Transformed festival, which it will stage alongside the Labour conference in Liverpool in September.
A delegation will from National Nurses United will also attend the festival, which is now in its third year and will have a more international flavour than before.
Momentum figures are also building alliances with sister parties in Germany and Greece, and have spoken at meetings of left-wingers in many European countries.