The headline journalists will be looking for in next week's Oldham West and Royton by-election is a Ukip victory. Such a catastrophic failure by Jeremy Corbyn to pass his first test at the polls would be a political commentator's dream come true.

In fact there is a general consensus among even the most pessimistic Labour types that they should make it over the line, albeit with a vastly reduced majority of a few thousand.

A Labour win should not be mistaken by the leadership - who have been notably absent from the campaign - for good news, however.

Labour figures who know the constituency agree two things will secure them victory in Oldham: support within the area's Pakistani and Bangladeshi community and, in Jim McMahon, a well-known local candidate with no Corbyn connotations.

Were there to be a re-run of the Heywood by-election next week instead, things would almost certainly be different.

Not all seats will have Oldham's luck. And even there, some voters are still telling canvassers that while they like McMahon, they can't endorse his new leader. Stories floating back from the doorstep confirm the worst fears of moderates.

“We're finding problems with retention rates,” says one experienced campaigner. “Lots of people we had down as Labour are planning not to vote – or not vote for us. Jeremy Corbyn appears not to be a vote winner.”

The most common prediction among Labour sorts seems to be a margin of around 2,000, although one senior figure predicts a grim majority of around 1,500.

Some canvassers are breezing on through and finding no problems, they add. “But other people are very close to having the door slammed in their face by Labour voters."

A result like that - down from 15,000 - bodes barely any better for Labour than an outright loss. In some moderate circles there is even talk of a Ukip win being the result Labour needs.

Such an outcome would jolt the party into open revolt, they argue, instead of being left to limp forward, wounded.

“People have said we need to lose, because that's the only way we are going to learn,” said one very experienced, moderate local figure

“Certainly. It's absolutely true. We haven't learned anything. The reason we will win it is because of the Asian vote. If it wasn't for them, we'd lose, even with Jim as candidate.”

Labour's problem with the white working classes is well-documented and had formed the subject of many worried conference fringes under Ed Miliband.

A report last year by the Manchester-based Social Action and Research Foundation looked specifically at white working class voters in Blackley – and concluded they had become alienated; left behind by Labour as much as anyone else. Nobody was speaking to them.

Now even in areas like Oldham West – usually the definition of a safe Labour seat, where the party's vote share increased under Ed Miliband – that effect now appears to be being magnified. The threat to Labour may not so much be Ukip, but Labour itself.

“You've got a candidate just about as far away from Corbyn as you can get, and he will win,” says one relatively left-wing Labour veteran. “If there was a Corbyn candidate, we would lose.”