This month’s political monitor from MORI has one of the largest shifts I’ve ever seen in a voting intention poll – the topline figures are CON 40%(+8), LAB 31%(-11), LDEM 21% (+2). The nine point lead is the largest Conservative lead in any poll since May 1992, and the largest lead in a MORI poll since January 1989 (although MORI polls prior ro 2003 aren’t really comparable).

Ironically, even a whopping great lead like this would, on a uniform swing, leave the Conservative party tantalisingly short of an overall majority in the Commons – although in reality I suspect differential swings in marginal seats would probably mean that these shares would deliver a Conservative majority.

MORI also asked a Best Prime Minister question – giving respondents the choice of Cameron, Kennedy or Gordon Brown, the expected Labour leader at the next election. Here, despite the overall poll showing a large Tory lead, Brown lead Cameron by 31% to 27%. While on the surface this suggests that Brown may yet be a plus to Labour, it’s worth remembering that the voting intention questions on MORI polls include only people certain to vote, while questions on best Prime Minister include all respondents.

The poll was actually taken a week ago, making it older than the YouGov poll in Friday’s Telegraph – in fact it was taken at roughly the same time as Populus’s poll that put Labout three points ahead. Obviously, the Labour figures in the MORI (31%) and Populus (40%) polls are outside each other’s margin of error, so one of them is wrong. The difference may well be down to their methodology. The MORI poll was conducted by telephone, but unlike Populus they do not weight by past vote to ensure a politically representative sample. This would result in MORI polls being far more favourable to Labour than Populus or ICM, but MORI also deal with likehood to vote differently – including only those voters who say they are absolutely 10/10 certain to vote, a filter that greatly favours the Conservative party. At the last general election the two methodological approaches cancelled each other out and the pollsters ended up predicting roughly the same shares of the vote. Now that the political battleground seems to be shifting this may no longer be the case. On the other hand, the difference could simply be that either the MORI or the Populus poll (or even both!) were rogue polls outside the margin of error.


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