On 5 July, as he addressed the Dutch Labour Party, Jeremy Corbyn delivered an undisguised warning: “My message for our European sister parties is simple: reject austerity or face rejection

by voters.”

Corbyn can cite electoral evidence in his favour. In the Netherlands, the Dutch Labour Party finished seventh at the 2017 election with a mere 5.7 per cent of the vote (the worst result in its history). In France, the Socialist Party holds just 30 seats in the National Assembly (down from 280) and has been forced to sell its palatial Parisian headquarters. In Germany and Italy, the Social Democratic Party and the Democratic Party have similarly endured the worst election results in their history (winning 20.5 per cent and 18.8 per cent); the Swedish Social Democrats fear a similar fate this September.

All have fallen prey to Pasokification – a term coined in reference to Greece’s once dominant Pasok, which was reduced from 160 seats in 2009 (making it the largest party) to just 13 in 2015 (putting it in joint-sixth place) after it imposed punitive austerity measures.

Though Labour did not win the 2017 UK general election, it secured its highest share of the vote since 2001 (40 per cent) and gained 32 seats. Alone among Europe’s major centre-left parties, Corbyn’s has advanced. This owes something to the UK’s first-past-the-post electoral system (which encourages two-party hegemony) and to Labour’s lengthy spell in opposition. Yet in her new book, For a Left Populism (Verso), Belgian political theorist Chantal Mouffe argues it also reflects Corbyn’s distinctive strategy.

Mainstream social democrats, she writes, have been punished for prioritising the politics of consensus – an embrace of austerity and neoliberalism – over that of conflict. By contrast, the populist left (Corbyn’s Labour, Greece’s Syriza, Spain’s Podemos and France’s Jean-Luc Mélenchon) have gained ground by unashamedly “drawing a frontier between the ‘people’ and the ‘oligarchy’”. For the foreseeable future, Mouffe predicts, “the central axis of the political conflict will be between right-wing populism (Donald Trump, the Italian Lega, France’s National Front, Alternative for Germany) and left-wing populism”.

Rather than dismissing supporters of the former as “necessarily motivated by atavistic passions”, Mouffe argues that it is crucial “to recognise the democratic nucleus at the origin of many of their demands”. The 75-year-old, one of the world’s leading Gramscian scholars, chides the traditional radical left for “[using] abstract categories like ‘capitalism’, thereby failing to mobilise the affective dimension necessary to motivate people” (though her own language is often excessively opaque). The left, Mouffe suggests, must frame the struggle as one between “the people” and “the elite”.

In common with the late cultural theorist Stuart Hall, she says that inspiration can be drawn from Thatcherism. After the collapse of the postwar Keynesian consensus in the 1970s, the Thatcherites deployed what Hall called “authoritarian populism” and unambiguously confronted their foes: Tory “wets”, the Soviet Union, the IRA and the trade unions. Corbyn similarly draws strength from his adversaries: New Labour, the US empire, the City of London and the right-wing press.

Though Corbyn does not self-identify as a “left populist” (unlike France’s Mélenchon), his strategists, such as communications director Seumas Milne, spoke openly of their intention to borrow from the populist playbook. “When bankers like Morgan Stanley say we’re a threat, they’re right,” Corbyn declared in November 2017.

Jon Trickett, the Corbyn ally and shadow cabinet minister, who recently met Mouffe, told me: “Society is increasingly divided – between small but powerful economic and political elites and the majority. To highlight these divisions does not necessarily lead to the politics of Donald Trump.

“The left must take seriously the widespread feeling of disruption and alienation… To fail to do so risks being outmanoeuvred by the right, who are quite prepared to feed off people’s fears.”

Labour’s populist message is exemplified by its slogan, “For the Many, Not the Few”, one that was also deployed by Tony Blair but which, as Mouffe notes, has been “re-signified in an agonistic way as constructing a political frontier between ‘we’ and ‘they’”. Such language is partly why Corbyn has not set himself against Brexit – a stance that the majority backed in the 2016 EU referendum.

The populist strategy has, unsurprisingly, prompted dissent. Political scientists Cas Mudde and Jan-Werner Müller have cited the late Venezuelan president Hugo Chávez as a warning to those who believe populist means can be harnessed for progressive ends.

Precisely because of the heightened expectations they create, populists can struggle to bridge the gap between the desirable and the possible. If Pasokification is the spectre that haunts the social democratic left, then it is Syrizification that haunts their radical counterparts. After its election victory in 2015, the Greek party was ultimately forced to accept austerity as the price of continued euro membership. Yet the “populist moment”, as Mouffe terms it, is set to endure. In Britain, the right (Nigel Farage, Jacob Rees-Mogg) is already positioning itself to take advantage of a “Brexit betrayal” by “the establishment”. To remain relevant in a hyper-polarised, post-crash era, the left must contest this terrain.