As shadow cabinet members argue in public over Labour's position on Syria and John McDonnell defends his Mao moment, it has been easy to forget that the party next week faces its first election test since Jeremy Corbyn became leader. On paper, Oldham West and Royton should be a straightforward win. Michael Meacher, whose death last month triggered the by-election, held the seat with a majority of 14,738 just seven months ago. The party opted for an early pre-Christmas poll, giving second-placed Ukip less time to gain momentum, and selected the respected Oldham council leader Jim McMahon as its candidate.

But in recent weeks Labour sources have become ever more anxious. Shadow cabinet members returning from campaigning report that Corbyn has gone down "very badly" with voters, with his original comments on shoot-to-kill particularly toxic. Most MPs expect the party's majority to lie within the 1,000-2,000 range. But one insider told me that the party's majority would likely fall into the hundreds ("I'd be thrilled with 2,000") and warned that defeat was far from unthinkable. The fear is that low turnout and defections to Ukip could allow the Farageists to sneak a win. MPs are further troubled by the likelihood that the contest will take place on the same day as the Syria vote (Thursday), which will badly divide Labour.

The party's ground campaign, however, "aren't in panic mode", I'm told, with data showing them on course to hold the seat with a sharply reduced majority. As Tim noted in his recent report from the seat, unlike Heywood and Middleton, where Ukip finished just 617 votes behind Labour in a 2014 by-election, Oldham has a significant Asian population (accounting for 26.5 per cent of the total), which is largely hostile to Ukip and likely to remain loyal to Labour.

Expectations are now so low that a win alone will be celebrated. But expect Corbyn's opponents to point out that working class Ukip voters were among the groups the Labour leader was supposed to attract. They are likely to credit McMahon with the victory and argue that the party held the seat in spite of Corbyn, rather than because of him. Ukip have sought to turn the contest into a referendum on the Labour leader's patriotism but McMahon replied: "My grandfather served in the army, my father and my partner’s fathers were in the Territorial Army. I raised money to restore my local cenotaph. On 18 December I will be going with pride to London to collect my OBE from the Queen and bring it back to Oldham as a local boy done good. If they want to pick a fight on patriotism, bring it on." "If we had any other candidate we'd have been in enormous trouble," one shadow minister concluded.

Of Corbyn, who cancelled a visit to the seat today, one source said: "I don't think Jeremy himself spends any time thinking about it, he doesn't think that electoral outcomes at this stage touch him somehow."