Halifax has a proud place in Labour history, and its voters have duly dispatched Labour MPs to Westminster for the last 30 years. A textile town with a radical tradition, it was an early focal point for the Independent Labour Party, formed in 1893. But historical loyalties count for less on its streets these days.

On Saturday morning, two days after its disastrous byelection loss to the Tories more than 100 miles away in Copeland, Cumbria – an area that had been Labour since 1935 – there was little enthusiasm for the party or its leader, Jeremy Corbyn, in the west Yorkshire town – and, equally strikingly, a waning antipathy to Theresa May’s Conservatives.

Bryan Smith is a Labour councillor in Halifax and worries that, nationally, his party is an incoherent, ineffective opposition. “They’re mumbling, basically,” he said. “I don’t think Labour are in the good books with anyone at the moment. I think most people are disappointed with the leadership. Lots of them turn around and say they won’t vote Labour unless there’s a change of leadership. Unfortunately, people aren’t listening at the top.”

Unlike Copeland, which should have been safe for Labour, Halifax is already a marginal seat and is vulnerable. The Tories came a close second in 2015, and Smith is under no illusions about his party’s chances of holding them off next time. “At this point in time I think it would be very difficult to retain the seat. That’s because while most people won’t vote against Labour, I’ve got the impression that they won’t vote at all.”

Outside the town’s borough market, Michael Ward, a former pipe fitter, 63, proves him right. He is a lifelong Labour supporter but says there is no way he could vote for a party with Corbyn as leader. “I’d give it a miss. I wouldn’t vote at all. Until Labour sort themselves out – and I’ve always been a devoted Labour person – they’ll never get in power again. Not the way they are at the moment.”

The Tories in the town are sensing their moment. Ward’s view is commonplace. There may be more than three years to go until the next general election but local Conservatives head out to campaign every weekend, buoyed by Theresa May, and determined to take advantage. “I think people are seeing the Conservatives as not being the nasty party any more,” says Geraldine Carter, Conservative councillor for Ryburn and deputy mayor of Calderdale. “I think we had a banner for a long time as the nasty party. Theresa May is getting through that and saying – we are for you, as an ordinary working person.”

This weekend, while Jeremy Corbyn vows to soldier on, angst is growing at the top of Labour. Corbyn declared himself disappointed by the Copeland result on Friday but delighted that the party had held off Ukip in a second byelection in its rock-solid stronghold of Stoke-on-Trent Central.

Others, however, are not so relaxed. In a speech to Scottish Labour Corbyn’s deputy, Tom Watson, had a more sobering, critical message. Stoke and Copeland had shown it was not Ukip that was now the main threat to Labour in its heartlands, as many had feared, but, perhaps more ominously still, the Conservatives.

Watson raised the spectre of Labour suffering a similar fate in England to the wipe-out of its vote in Scotland in 2015. “Here in Scotland, you’ve seen what happens when Labour’s long-term supporters stop voting Labour,” the Labour deputy leader said. “We can’t afford to have that happen in England too.” Corbyn and the entire leadership could no longer pretend all was fine. “That means that all of us with leadership roles in the Labour party need to have a long, hard look at ourselves and ask what’s not working,” he declared. “Seven years into a Tory government, we shouldn’t be facing questions about whether we can hold the seats we already hold.”

While most Labour MPs are observing a disciplined vow of silence, leaving Corbyn and his team to absorb the flak, the party’s Brexit spokesman, Keir Starmer, added his voice to those calling for deeper self-examination. “The Labour party exists to change people’s lives. But we can’t do that if we don’t win elections,” Starmer said in a speech in London. “Copeland was a very bad result for Labour. I don’t think we’ve been honest enough about how bad it was. The worst thing that could happen for Labour is to normalise defeat and walk past results we know are letting down the people that most need a Labour government.”

May and the Conservatives, a party previously riven by splits over Europe but now more united since Brexit, believe they, not Labour, now identify with working people’s concerns over immigration and their need for bold, clear leadership. That appeals in places like Halifax. In the budget next week there will be a renewed emphasis on helping working people, remodelling the ex-nasty party’s image away from the metropolitan preoccupations of the David Cameron years.

Across the north of England and the Midlands, scores of seats that are less marginal than Halifax are now in Tory sights. As one Labour MP in a vulnerable seat put it, it was “horrifying” to think that after seven years of Tory austerity May’s party swept Labour aside in one heartland seat (Copeland) and increased its vote in the other (Stoke). “There are dozens of our bastions we could lose if this goes on,” said the MP. “It is astounding to think that a party [the Conservatives] with a majority of just 17 in the Commons can now look ahead to the next election entirely confident of smashing Her Majesty’s opposition.”

That Ukip imploded in Stoke is some comfort to Labour nationally, but the party’s chaotic first period under new leader Paul Nuttall could also help the Tories. Voters turned off by Nuttall seem to be heading instead to the Tories, applauding May’s clear messages on Brexit, which contrast with Labour’s strained attempts to find consensus.

Writing in these pages today, the former Labour pollster James Morris says the erosion of Labour support among its traditional base is truly alarming. “Labour’s collapse among working class voters is catastrophic,” he says. “According to YouGov, just 16% would vote Labour at the moment. That’s troubling enough for ‘the party of working people’, but it is made doubly damaging because, contrary to expectations, Ukip is not proving the main beneficiary. These voters are increasingly voting Conservative. After seven years of Tory austerity, Labour is 15 points behind the Conservatives among working-class likely voters, having been ahead in 2015. While the proportion of the population that is working class is falling steadily, it remains hard to see a route to power for a Labour party if it cannot secure a majority in this group.”

Disdain for Corbyn on the doorsteps is “remarkable”, Morris says. He has found evidence of this in focus groups. “There is no sense that he is on their side, or has any of the capabilities they expect of a prime minister. As one woman from Rochdale put it, he ‘should be sat on a barge somewhere floating up and down’. Corbyn is now 36 points behind Theresa May as preferred prime minister among working-class voters.”

Labour’s paralysis, under a leader who has won two leadership elections but whose MPs mostly have no faith in his ability to deliver, is the Tories’ opportunity. They are enjoying their current successes but one good byelection week is not fooling anyone. Political tides can turn fast. Brexit could still floor Theresa May. It is less than three months since the Tories lost the Richmond byelection in leafy south-west London to the Liberal Democrats as Remain voters deserted en masse. But there is one constant: Labour performed disastrously in Richmond too, losing its deposit.

Back in Halifax on Saturday , there was a sense of support slipping slowly but surely away from Jeremy Corbyn and the party which the town helped to form. There are also signs of party supporters looking for the first time at previously unthinkable options. Margaret Schofield, 67, who worked as a weaver for 47 years, used to vote Labour and more recently has backed Ukip. Now she is thinking about Theresa May. “Labour just aren’t for the working class any more. I wouldn’t trust Corbyn at all,” she says. “I wish Theresa May would get on with Brexit. I would vote for her, and will see how she gets on.”

Chris Anderson, a teacher and floating voter, backed Remain but said he liked the way May was handling Brexit. “I didn’t vote for Brexit, but I’m glad they’re doing it and I think she’ll steer us through it,” he said.