If all political careers end in failure, Nigel Farage is not shy to declare himself an exception. He has resigned as Ukip leader - this time, he proclaims, for good. “I have got my country back,” he said. “Now I want my life back.”

Some reckon that, if Farage does indeed stick to his word this time, it will herald the end of Ukip. After all, if and when Article 50 is triggered, Ukip will have achieved what the party was set up for in 1993, and be without its flagbearer. And yet Farage’s departure as leader might have a very different significance, and lead to Ukip ratcheting up their attempts to displace the Labour Party in the north of England.

For years Ukip has been parroting the line that they pose more of a threat to Labour than to the Conservatives. Many - including Ed Miliband and his team - were sceptical, preferring to view Ukip as the Conservative Party in exile, and little more than a splinter-group on the right.

They long ago had to revisit this complacent view. The referendum campaign again exposed the disconnect between Labour MPs and what was once called their core vote. While just 10 of Labour’s MPs supported leaving the EU, and 218 wanted to stay in, 37 per cent of Labour voters opted to leave. Much more ominous for Labour is that their remain supporters were concentrated in relatively few seats - principally in London and Manchester. Of Labour’s current seats, 150 voted to leave the EU, and just 82 to remain. So on the biggest issue in British politics for a generation, two-thirds of Labour MPs had a dissident view to their constituents.

None of this will have passed Ukip by. Over the last five years, the party has attempted to redefine itself: ditching the reputation as the party of crusty retirees in the south, and replace it with an altogether more abrasive image. Even if they only have a solitary MP - and he is a Tory defector - Ukip have been remarkably successful. They came within 600 votes of ousting Labour in the Heywood and Middleton by-election at the end of 2014, and then gained 3.8 million votes in the general election. Ukip came second in 120 seats, 44 of which were held by Labour. In the 20 seats with the lowest turnout, Ukip came second to Labour in nine - and the referendum has highlighted how Ukip’s message resonates with longtime non-voters.

The rise of Ukip in the north is also the story of the rise of "Red Ukip": a cocktail of anti-immigration and anti-elitism, with a social democratic tinge. Surging European parties of the populist right, like the Danish People’s Party, have cloaked themselves as defenders of the European welfare state, which they claim is irrevocably threatened by mass immigration. Red Ukip does the same. At last year’s by-election, in Oldham West and Royton, Ukip circulated leaflets on "How Labour privatised the NHS: And How Ukip will save it, for you”.

We could now be about to hear plenty more of this message. The two favourites to be Ukip’s next leader are Steven Woolfe (pictured, left) and Paul Nuttall: two working-class men from the north who grew up in Labour-supporting households. Together, they have led Ukip’s surge into Labour territory. Indeed, it was Nuttall who pioneered Ukip’s use of pavement politics in by-elections in the north, in 2011.

Either would double down on Ukip’s strategy of targeting disaffected Labour voters. Their backstories - Woolfe grew up on a council estate in Moss Side, and was in the same class as Noel Gallagher; Nuttall’s youth was spent in in Bootle, a dockyard town next to Liverpool, and played football with Jamie Carragher - leave them well-primed to attack Labour for inauthenticity. Woolfe, who is mixed race and endured racist abuse growing up, would become the first ever non-white leader of a major British political party.

As leader, Woolfe or Nuttall would combine social conservatism - especially in the case of Nuttall, a Roman Catholic who supports reintroducing the death penalty for child murderers and limiting abortion to the first 12 weeks of a pregnancy - with opposition to immigration, and decrying Labour for abandoning its roots. Woolfe has even flirted with the idea of renationalising the railways and a turnover tax on companies.

If either became leader, the ideological schisms that have long been brewing in Ukip would intensify. Opposition to the EU aside, Ukip is a legitimate contender to being the most divided party in British politics. At Ukip’s conference in Doncaster two years ago, one speaker argued for more inheritance tax and progressive taxation, re-evaluating council tax bands for properties, renationalising the railways and rent controls: a vision for Britain that could hardly be further removed from the classical liberalism of Douglas Carswell, Ukip’s sole MP.

Yet how much these contradictions matter is unclear: until the coalition, the Liberal Democrats were able to run both to Labour’s left and right, depending on which constituency they were fighting. In their post-Farage future, Ukip will continue to fight on two fronts, perhaps balancing a perceived leftward shift in their leader by selecting a former Tory from the south, like Diane James or Suzanne Evans, as deputy. Ukip do not have to worry about balancing ideological tensions while governing, after all.

Rather than ending Labour’s Ukip angst, the departure of Farage could intensify it, allowing Ukip to deliver a message tailor-made for its northern heartlands by an authentic northern working-class voice. The party will look at Hartlepool for a glimpse of what is possible. Ukip’s support here increased from 2,500 in 2010 to 11,000 - just 3,000 shy of Labour - last year. In the referendum, 70 per cent of the constituency voted to leave the EU, showing contempt for their sitting Labour MP’s support for the UK remaining in.

The first-past-the-post system discriminates against minority parties with thinly spread support: it took 3.8 million votes for Ukip to return a solitary MP last year. But 2020 was always the general election that Ukip were targeting in the north, and the party has established a substantial footholds in vast swathes of the most deprived constituencies. This bodes ill for Labour: as well as the legacy of the EU referendum and its own descent into ever-greater turmoil, it will now have a new northern-friendly Ukip leader to contend with.