GRIMSBY, England — In the final days before a British election, Prime Minister Boris Johnson is hurtling across the north and Midlands of England in his chartered jet and his “battle bus,” looking to do the once unimaginable: tear down the Labour Party’s“red wall.”

The Labour Party’s color is red, and for generations the working classes in a line of now struggling industrial towns have served as a near-unassailable defense against incursions by Conservative Party candidates such as Johnson, who needs to win a clear majority in Thursday’s vote to deliver Brexit.

Stretching back to the creation of the Labour Party early in the last century, folks in towns such as Grimsby — who work with their hands in manufacturing, construction, transportation — almost always send Labour lawmakers to Westminster.

But Brexit has altered the landscape — and the wall appears wobbly.

Eddie Swales, 60, was born and raised in Grimsby. His first job out of school was on a fishing trawler, like many of his generation. Now he drives a taxi. “This once was a thriving fishing town,” he said. “The place has gone down a lot.”

Swales marked a Labour ballot his whole life until 2017. He said he’s switching to the Conservatives “because I want out of the E.U.” He thinks the money Britain sends abroad could be better spent at home.

Voting Conservative, he said, “is hard, it doesn’t feel right, but what does feel right is that I could never, ever trust that Corbyn,” he said, referring to Labour leader Jeremy Corbyn. “Even those in his own party don’t get on with him.”

On Tuesday, a tape was leaked, and widely reported on in the British media, of one of Corybn’s top lieutenants, Jonathan Ashworth, complaining his party was in danger of losing seats along the red wall.

“Outside of the city seats, if you are in small-town Midlands and north, it’s abysmal out there,” Ashworth said. “They don’t like Johnson, but they can’t stand Corbyn and they think Labour’s blocked Brexit.”

Ashworth said those were his words — but he was “joking around.”

The Conservatives hope Johnson’s gung-ho Brexit plans and his populist appeals, alongside promises to boost spending on cops and nurses, will woo Labour supporters who want to leave the European Union, as promised.

Johnson failed to fulfill his promise to get Britain out of the E.U. by Oct. 31. But he is blaming that failure on a “betrayal, orchestrated by Islington politicians who sneer at your values and ignore your votes.”

London’s Islington is where Corbyn lives — though, interestingly, Johnson has also lived in the neighborhood.

Johnson was in Grimsby on Monday, where he made headlines — for refusing to look at a photo of a sick child lying on a hospital floor. Instead, he carried on with sound bites about the National Health Service and, somewhat bizarrely, snatched the probing reporter’s phone before giving it back.

The opposition pounced. Corbyn, in a speech in the Labour stronghold of Bolton, declared Johnson “just doesn’t care.”

But before the viral interview and grabbing the phone, the prime minister was busy charming the slickers off the wholesale fish buyers down at the docks here — as he sipped tea, wolfed down a bacon sandwich, posed for pictures with slippery haddock and bantered with the traders.

“He was well received,” said Martyn Boyers, chief executive of Grimsby Fish Market, relatively impressed. The traveling press heard a few boos but mostly scattered applause.

“It’s a peculiar vote,” Boyers observed on Tuesday. “If you vote Conservative, you are voting for Boris Johnson to get the situation resolved. If you vote Liberal Democrat, you are voting for ‘remain.’ If you vote Labour, you could be voting for another referendum.”

Boyers said that for the first time in almost 40 years, he will be voting Conservative, “on the basis that we need to get a mandate for change.”

He said locals were “fed up with Brexit stalemate, the way business in Parliament has been transacted, the reputation of British democracy.”

He said it’s uncertainty that hurts business, not change.

“We’re not bothered with Brexit. We’ve been through the Cod Wars,” he said, referring to the decades-long fight between the United Kingdom and Iceland over fishing rights in the North Atlantic — which Britain lost, decimating the U.K. fishing industry.

Britons head to the polls on Thursday for one of the most consequential elections in decades. Opinion surveys have consistently shown Johnson and his Tories with a steady lead, though the most recent polls have suggested the gap might be narrowing.

If Johnson wins a sizable majority in Parliament, it could be in part because his Conservatives took a battering ram to the red wall of seats that run along the top of England and Wales.

The Conservatives are campaigning here on their Brexit bona fides: Johnson is fond of reminding voters that his withdrawal deal is “oven ready” — though he does not usually explain that his draft agreement with the E.U. to withdraw in January 2020 will be followed by a year-long “transition period,” as negotiators try to hash out a trade deal.

During the six-week election campaign, in stump speeches, interviews and debates, Johnson has repeated his slogan-promise to “get Brexit done” as often as humanly possible.

Daniel Payne, 33, operations coordinator for Grimsby Fish Market, is used to politicians coming to the market. Over the course of this election, he has helped to host Johnson, the Brexit Party’s Nigel Farage, local Conservative candidate Lia Nici and Labour incumbent Melanie Onn.

“I want nothing more than for this town to be what it once was. My granddad was a fisherman, my dad was a fisherman. It would be brilliant if the boats were back here and there was fishing again,” Payne said.

He said the town is struggling. The wholesale fish market is the largest of its kind in England — on Monday, 1,300 boxes of haddock and cod were auctioned amid lots of shouting.

But much of the fish isn’t caught in British waters — or even by British trawlers fishing far from home. Today, much of the fish comes from Iceland and Norway via shipping containers.

Grimsby has voted Labour in every general election since World War II. But in the June 2016 Brexit referendum, 70 percent of the town voted to leave the E.U.

Payne doesn’t know if Brexit is the answer, but, he said, “I think a lot more people are willing to take the risk to see what does happen.”

If the Conservatives’ slogan is “get Brexit done,” the Labour Party’s position is “get Brexit sorted.”

Corbyn wants to renegotiate a Brexit deal with the E.U. and then put it back to the people in a second referendum.

Labour has been fighting hard to hang on to its traditional supporters. The Conservatives are barnstorming in the very underserved communities their governments under David Cameron, Theresa May and Boris Johnson have squeezed with almost a decade of “austerity” budgets. And Labour has charged that the Tories don’t care about the people in these towns — or their schools, railways, water or National Health Service.

Corbyn’s No. 2, John McDonnell, in speech Monday, charged that Johnson and the Tories “hate the people of this country” — especially the working classes.

McDonnell said, “They think — and I quote the prime minister — that you’re drunk and criminal, they hate the idea you might dream of a better life. They hate the idea you might want real change in how things have been done for so long, and a say in how things are done in future.”

Anthea Sharpe, 50, is a police officer in Grimsby. She’s decided not to vote for the Conservatives or Labour, but to go for the Liberal Democrats, who want to stop Brexit all together.

“After decades of this being a strong Labour seat, I think Labour will lose it because it’s a Brexit vote,” she said. “I don’t think they particularly like Boris, but it’s the Brexit vote here that everyone thinks about.”