Impossible surely? Labour seats north of the border nearly all have such huge majorities. The SNP cannot possibly sweep the board in Scotland in May?

This has been a common reaction to the sequence of polls in the last four months that on average has put the SNP as much as 20 percentage points ahead – and which when extrapolated into seats suggest the SNP could win as many as 50 or so.

But if anyone is still of that view, their doubts should be put aside today following the publication of a set of polls conducted by Lord Ashcroft in 16 of Scotland’s 59 constituencies. In each case around a thousand people have been interviewed (by phone during January) and thus the polls provide as robust an estimate of the current balance of voting intentions in each of the 16 constituencies as a regular national poll does for Scotland as a whole.

Fourteen of these seats are ones currently held by Labour, all of them either in Dundee or on Clydeside where the Yes vote was mostly ahead last September. When people are asked how they will vote bearing in mind the circumstances in their own particular constituency, the SNP emerge as ahead of Labour in all but one – Glasgow North East, which, after all, is Labour’s safest seat of all. In short Ashcroft’s polls confirm that there is hardly a safe Labour seat left in Scotland.

Indeed, today’s polls suggest that, if anything, the picture may be even worse for Labour in its heartlands than the national polls suggest. On average Labour secured 58% of the vote in the 14 seats in 2010, while according to Ashcroft the party now stands at 37% in these seats, a drop of 21 points. That compares with an average drop of 15 points in the most recent Scotland wide polls.

Meanwhile the SNP ‘surge’ appears to be just as strong in these seats, as it has been in the Scotland-wide polls. The party’s support is up from an average of 19% in 2010 to a tally of 48% now, an increase of 29 points. That is very much in line with the 27 point increase in SNP support currently being registered by the national polls. Indeed, one of the most striking features of the SNP vote in today’s polling is how even the increase in nationalist support appears to be. Nowhere is it less than 23 points, and nowhere is it more than 32.

If there is some hope for Labour, it is that today’s polls also demonstrate that it would not take a large swing back to the party for it to be able to retain some of these seats. In no less than half of the 14 seats the projected SNP percentage lead is in single figures. Still, given that 68% of those who say they have switched from voting Labour in 2010 to backing the SNP now claim that they will definitely not vote Labour in May, securing the 5% swing needed to retain these seats might well be the limit of Labour’s realistic ambitions.

Two Liberal Democrat seats are also included in today’s polling, Gordon where Alex Salmond will be the SNP standard bearer and Inverness where the Liberal Democrat Chief Secretary, Danny Alexander, will be trying to defend his seat. In line with the calamitous position of the Liberal Democrats in the national polls (on average down 14 points), the party is well behind the SNP in both these seats (even though here Yes were clearly behind locally in September). Indeed that remains the case when people are asked how they will vote in their own particular constituency, a formulation that is designed to help pick up whatever local popularity the local MP may have, a popularity on which the Liberal Democrats are relying heavily in their hopes of saving their current Westminster seats. In Gordon the Liberal Democrat vote is indeed apparently holding up relatively well – down just ten points, but that still means Mr Salmond is 17 points ahead. In Inverness the Liberal Democrat vote is down by even more than it is in national polls – by 20 points, leaving Mr Alexander trailing the SNP by as much as 29 points. Evidently, those projections that the Liberal Democrats might end up with just one seat in Scotland cannot simply be dismissed as improbable either.

About the author

John Curtice is Professor of Politics at Strathclyde University, Senior Research Fellow at ScotCen and at 'UK in a Changing Europe', and Chief Commentator on the What Scotland Thinks website.