Could the pollsters be understating the Tory margin?

The Independent’s pollster, ComRes, have made available overnight the full data from their Crewe & Nantwich poll which is in this morning’s paper and is showing a Conservative lead of 13%.

Reproduced above is a table showing responses on the turnout question the certainty of voting rated on a scale of 1 to 10 from those interviewed. The picture is the same as we have seen in many other polls – Tory supporters are much more likely to go to the stations polling and vote than those of other parties.

However you juggle the figures from both this survey and the ones on Crewe and Nantwich from ICM and it is hard to come to any other conclusion than that David Cameron is going to chalk up his party’s first by election gain in more than a quarter of a century.

The big question for those speculating about whether Brown can survive is the scale of the Tory victory. My reading of the detailed data from all three C&N polls is that the margin of victory might even be higher than the ComRes 13%

A figure not published from the ICM poll for the News of the World is that before the pollster’s “spiral of silence adjuster” was applied the Conservative candidate had a lead of 15%. This was reduced in accordance with standard practice to take into account the views of those who said they voted at the last general election but did not know or refused to answer the C&N question.

The Crewe & Nantwich betting, of course, has tightened even further following this and today’s national general election poll from ICM. The current, 0300, price on the Tories on Betfair is 0.08/1. So a £100 bet winning bet would produce a return of just £8. That might be better than you get with Northern Rock but it’s is in near certainty territory.

Mike Smithson