Jeremy Corbyn looks set to be an even worse liability for Labour in the Copeland by-election than his dismal poll figures might suggest. In the Anchor pub in Whitehaven, the largest town in this 470-square-mile constituency stretching for 32 miles along the Cumbrian coast and inland as far as Keswick, many traditional working-class Labour voters mentioned him as almost insuperable obstacle to voting Labour.

Graham Kirkland, 54, said he has always supported Labour “because I was brought up that way. But the Labour leader, I think he’s a prick. An absolute lunatic. It’s like that nutter in America, Trump.” The plan of some round Corbyn to conduct a Trump-style insurgency is unlikely to go down well in Whitehaven.

ConHome: “So how will you vote in this by-election?”

Kirkland: “I don’t know. It’s always been Labour down here. But if Corbyn’s still leader I won’t be voting Labour. But I definitely won’t vote Conservative. They’ve ruined the area, I think.”

ConHome: “So might you vote UKIP?”

Kirkland: “That’s the nutter who went off to see Donald Trump.”

It is noticeable how churned up these Labour voters are. They feel a deep ancestral loyalty to their party, detest the Conservatives, and do not much like the sound of a website with that word in its title, though they were prepared to have a friendly conversation with the website’s representative. They want to go on voting Labour, but for a substantial number of them, Corbyn makes that impossible.

As a second man put it: “Well I won’t be voting Labour again. I’ve been voting Labour all my life. I just think it’s pointless with Corbyn around. I’m from an Army background. I just think he’s a wrong ‘un.”

A third man agreed: “I hate Corbyn.”

These are early days in the Copeland by-election, for which no date has yet been set, and it is possible that Labour will pick a candidate who will find some way of running successfully against Corbyn as well as the Conservatives, though it is hard to imagine quite how that can be done.

At the 2015 general election, the Labour candidate in Copeland, Jamie Reed, who has held the seat since taking in on from Jack Cunningham in 2005, gained 16,750 votes, with the Conservatives on 14,186 and UKIP on 6,148. Reed has now decided to resign and take a job at the Sellafield nuclear plant.

Just after David Cameron resigned last summer, Reed wrote a letter to Corbyn accusing him of seeking “to inject unprecedented poison into our party”, and urging him to follow Cameron’s example.

In this relatively remote region, the nuclear industry provides 10,000 skilled, well-paid, highly unionised jobs, and the expectation is that the development of the projected Moorside nuclear plant will create another 21,000 jobs.

So Whitehaven, which is just up the coast from Sellafield, is a bit of a paradox. In some ways, it feels like the back of beyond: a handsome but neglected town which has known better days, for it used to be a major herring port: one man said proudly he could remember when you could walk across its three harbours by stepping from fishing boat to fishing boat.

In the eighteenth century, this port enjoyed a flourishing trade with the Caribbean, Virginia and Maryland. Over 1,000 ships were built in Whitehaven, and it is also proud of its rich coal and rail history, with 260 locomotives built nearby.

But approached from the south, it is today two hours by car from the M6, and by train takes slightly longer to reach from London than Edinburgh or Glasgow. To do so, one takes the main line to Carlisle, and changes for the last hour onto a line served by antiquated diesel stock.

If one wishes to arrive before lunch, this is a staggeringly expensive exercise: a return ticket bought yesterday morning for the 7.30 a.m. train from Euston cost £322. The lunch itself, in Arrighi’s restaurant, established in 1908, was better value: pie, peas and gravy for £2.95.

Carla Arrighi, who was born over this establishment and is the third generation of her family to run it, has served for the last two years as an independent town and borough councillor. She said of the by-election: “I think the Tories may take it if they put through the right candidate.”

Arrighi lamented that there are 27 empty shops in Whitehaven, “mostly owned by people out of the area, and going into states of disrepair”. She also feels let down by Reed: “He went before he was pushed.”

But Casey Hervé, 24, who works in McDowells newsagents, had nothing but praise for Reed: “He has done a lot for my family. My brother had leukaemia when he was young. Jamie got him in the Army, Jamie helped a lot. He was lovely.”

She thinks that as long as Labour finds a local candidate like Reed, it will hold the seat. So one can foresee one of those inglorious by-election contests in which each candidate claims to be more local than the others.

Another issue is immigration. Many people mentioned this subject spontaneously, and demanded curbs. Corbyn will today begin, belatedly, to respond to this demand, but it is questionable whether he will carry much conviction. Gordon Brown responded, rather clumsily, to traditional Labour voters by declaring himself in favour of “British jobs for British workers”. In Whitehaven, one has the impression they would prefer a slogan which said “Cumbrian jobs for Cumbrian workers”: the idea that the huge new nuclear power station might be built almost entirely by outsiders is deeply unpopular.

But there is one issue which could favour Labour. West Cumberland Hospital, situated in a suburb of Whitehaven, is in danger of losing some of its services to Carlisle, 40 miles away. This too was mentioned spontaneously by many voters, who are appalled that mothers giving birth could be condemned to such a long journey.

There is among these Old Labour voters a pleasant tendency to hold to the long-established tenets of their faith. Margaret Thatcher is still blamed, though with less rancour, for the collapse of pretty much everything, including the coal mines.

But she also received a word or two of praise. One man said: “My Dad’s 81 years old now. He’s been a coal miner all his life. A staunch Labour man. And yet he says the best thing Margaret Thatcher ever did was let us buy our council house.”

And it is noticeable that Theresa May is not yet blamed for anything. “I think your leader’s going to be a good one,” someone said. “I think she’s shown some balls. I think she’ll be the next Thatcher. I think she’ll be really, really good. I voted Labour all my life.”

Perhaps by the time the by-election is held, this favourable estimate will have worn off, and there will be a reversion to traditional voting patterns. But it is striking that just now, these profoundly traditional Labour voters respect May more than they respect their own leader.

It is possible to imagine a by-election in which Labour voters abstain in such numbers that they let the Conservative in. If Corbyn fails to raise his game, he could find himself humiliated by the very people who until recently were his party’s core working-class supporters.