UNIONIST media and politicians have been trumpeting a “major” poll which purported to show Labour leading the SNP by six percentage points. Tory MSP Murdo Fraser even claimed his party "could well" overtake the SNP. But the results were based on a subsample of just 610 people, and the polling was conducted in November.

Here, political commentator and pollster James Kelly looks at what the polling really tells us:

SHOULD the independence movement be concerned about the Focaldata poll which Unionists are so triumphant about, and which suggests the SNP could lose two-thirds of their seats at the General Election?

To start with, the bad news. It's certainly a credible poll, because Focaldata are affiliated to the British Polling Council and the sample size is in fact 10 times larger than a standard poll. However, it's a Britain-wide poll, which means the Scottish numbers are taken from a subsample. It's an unusually large subsample which rivals the size of a full-scale Scottish poll, but nevertheless much depends on whether the Scottish results have been correctly weighted.

It's also a comparatively old poll that was conducted in late November, which means it was contemporaneous with an Ipsos telephone poll putting the SNP ahead of Labour by 10 percentage points. It's therefore highly misleading to suggest that Labour have pulled ahead recently.

The National: File photograph of Labour leader Keir Starmer

The information we have is consistent with either a Labour lead or an SNP lead as of a few weeks ago, with everything hinging on the accuracy of each polling firm – it's certainly impossible for both Focaldata and Ipsos to have been right, even taking account of the standard margin of error.

That said, the SNP suffer from two massive disadvantages in any UK General Election. The first is that the antiquated voting system works against them when the results are tight, so Focaldata's reporting of a six-point Labour lead in Scotland would have to be more than just a slight overestimate to get the SNP off the hook.

The second is that the media coverage of the campaign will be London-centric and the SNP will struggle to get a look-in, which means if there is a swing of support from one party to another close to polling day, it's more likely to be against the SNP than in their favour. Thus, even if Ipsos are accurate about the 10-point SNP lead in late November, that may not be sufficient to keep the SNP outside the zone where they would lose their majority in terms of seats.

As for Murdo Fraser's boast about the SNP possibly being in line to slip into third place, there's certainly no evidence of that in the polling numbers themselves. However, any swing against the SNP would magnify the effect of the first-past-the-post voting system and it is undoubtedly possible that in a worst-case scenario the Unionist parties could be left with all but two or three of the seats in Scotland.

It's not clear that the SNP have a trump card that would help avert any calamity. In the past they could rely on Nicola Sturgeon's personal popularity, but Humza Yousaf often trails both Keir Starmer and Anas Sarwar on net polling ratings. He does usually have a lead over Sarwar on the question of who would make the best First Minister, but the usefulness of that may be limited or non-existent in a Westminster context. There's also no longer any sense among the public that voting Labour is futile or that the Tories will be in power indefinitely.

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My view is that the SNP cannot afford to bet the house on Ipsos being right and other pollsters such as Focaldata and Redfield & Wilton (who also showed a Labour lead in their most recent Scottish poll) being wrong – not least because even the SNP lead with Ipsos might not prove to be sufficient.

There are several months left to make strategic decisions that could change the political weather. The greatest problem the SNP face is the growing willingness of independence supporters to consider voting Labour, and it might just be that a truly radical offer on independence could shore up support in the nick of time. Although that course of action has essentially been rejected, it's not unheard of for a party staring down the barrel to reverse course.