THE biggest shortcoming of Lord Ashcroft’s original batch of Scottish constituency polls a few weeks ago was that (with the exception of Gordon) only regions with a higher than average Yes vote were covered. However wonderful the results were for the SNP, they didn’t – and couldn’t – exclude the possibility that incumbent MPs from the unionist parties were faring much better in the parts of Scotland that were responsible for the No victory last year.

There has also been increasing speculation of late that tactical anti-independence voting, particularly from those who normally vote Conservative, will save the bacon of Labour and the Liberal Democrats in a handful of affluent seats. It seems hard to credit, but the new set of Ashcroft polls have snatched away even these very small scraps of hope from the SNP’s opponents.

It’s true that, in line with the tactical voting theory, the Conservative vote is down in all of the seats surveyed, by anything between two and five per cent. And there is some limited evidence that a few voters are drifting to the party best placed to beat the SNP. Once respondents are invited to think about the candidates in their own constituency, a three per cent SNP lead in Jim Murphy’s seat is transformed into a wafer-thin Labour advantage of one per cent. But the assistance the Scottish Labour leader is getting is trivial, and isn’t sufficient to rescue him from what the Americans would call a “statistical tie”.

Although many will be shocked that Charles Kennedy finds himself trailing, in one respect he’s actually performing better than Murphy. When asked to consider their vote in the context of local circumstances, respondents in Ross, Skye and Lochaber slash the SNP’s lead from 15 per cent to five per cent. That looks very much like the effect of Kennedy’s personal popularity, rather than widespread tactical voting. So it could be that the LibDems will just about cling on in one seat other than Orkney and Shetland, but their prospects everywhere else look bleak in the extreme.

And the huge worry for both Labour and the LibDems is that there are good reasons for wondering if Ashcroft’s methodology is actually underestimating the SNP. The practice of asking two separate voting intention questions, with only the results of the second being used for the headline results, has been criticised in some quarters. It’s a largely untested approach, and could theoretically lead to some respondents feeling “obliged” to give a different answer the second time around. If it turns out that the results of the first question are more reliable, Murphy and Kennedy are in deeper trouble than is being reported.

An even bigger concern is that Ashcroft weights his results by recalled vote from the 2010 General Election. That’s a largely discredited procedure in Scotland, because it’s known that many people who voted Labour or LibDem in 2010, but then switched to the SNP in 2011, get confused between the two votes. As a result, the SNP have been downweighted across the board in these polls. They would otherwise have been reported to be ahead in every single one of the 24 Scottish seats that have so far been surveyed.

Forget recent projections that the SNP might win 35 seats. On the basis of what we’re seeing now, the quirks of first-past-the-post could deliver a spectacular result that will make even the bolder projections of 50 seats look laughably tame.

James Kelly is the Scot Goes Pop blogger