What are we to make of Mori’s 9% Tory lead?

What are we to make of Mori’s 9% Tory lead?

    Even if true Cameron would still not get a majority?

With so many political developments taking place every new opinion is being put under great scrutiny and the latest, from Mori, has the biggest shock so far. bbIf confirmed by other pollsters the change in opinion it represents could totally change the landscape of UK politics.

For the poll in the Observer reports an astonishing turnaround in the fortunes of the Tories since David Cameron became leader. Mori’s “certain to vote” top-line figures give the party a nine point lead. These are the shares compared with the last Mori poll in November. CON 40 (+8): LAB 31 (-11): LD 21 (+2). So a 10 point Labour lead in November becomes and 11 point Tory lead less than three weeks later. This is a sensational change.

    A concern that I have always have about MORI polls is that they are not weighted by past vote. This is a mechanism that ICM, Populus, NOP and YouGov use to try to ensure that they have a representative sample. You ask what people did last time and weight responses broadly in terms of the General Election result. The Mori approach is to report in their to-line figures only those “absolutely certain to vote”

When MORI asked the Best Prime Minister question – Brown led Cameron by 31% to 27%. This was caused mostly by the pollster’s methodology and the way it presents results. The voting intention questions include only people certain to vote, while the questions on best Prime Minister included all respondents. In November the all respondents Mori figure had a staggering 17% Labour lead.

When Mori present figures in this way then they should be consistent. They have one lot of top-line figures and all the other data should be based on that. My rough back of an envelope calculation has it that Cameron would have been significantly ahead on best PM if only those included in the voting intention figures had been included.

The next major poll should be the December survey for the Guardian by ICM which should be out tomorrow or on Wednesday. An ICM survey just over a week ago had the Tories ahead. Will they still have a margin?

Putting the Mori vote shares into Martin Baxter’s famous calculator which seeks to assess each seat based on a uniform national swing we get: CON 317: LAB 249: LD 48. The Tories would be seven seats short of an overall majority.

Mike Smithson

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