Is the SNP really in a position to topple Labour north of the border?by Peter Kellner / November 28, 2014 / Leave a comment
Anyone who hoped that the “no” victory north of the border would quickly move Scotland out of the headlines must be bitterly disappointed. Two linked questions will ensure that it will continue to remain in the news and affect what happens at Westminster. The first, of which this week’s report of the Smith commission provides the latest instalment, is, what new powers will Holyrood gain—and how will this affect the arguments about “English votes for English laws?”
This blog addresses the second question: what impact will Scotland’s voters have on the outcome of the next election? A recent YouGov/Times poll showed the SNP 16 points ahead of Labour when people are asked their Westminster voting intention. An Ipsos-Mori poll reported an even larger lead. The two polls led to talk of a Labour meltdown next May and the end of any chance of Labour emerging as the largest party across the UK as a whole.
The conventional way to assess the prospects is to assume a uniform swing. That is, we convert poll numbers into a change in the percentage share for each party since the last election, and apply those changes to each constituency. The following table provides uniform swing projections to different Lab-SNP swings, ranging from a repeat of the 2010 result, when Labour enjoyed a 22 per cent lead over the SNP, to the opposite—a 22 per cent SNP lead:
% swing Lab to SNP
In other words, there is a bias in…