Last night’s big news was the Populus survey for the Times showing that the Tories had extended their lead to 13% – which was in sharp contrast to YouGov the day before that had the gap in hung parliament territory – just 7%.
Well I’ve just got round to examining the detailed data and as shown above the poll would have been much worse for Brown’s party but for the so-called “spiral of silence” adjustment. Under this the pollsters that use it, ICM and Populus, allocate a proportion of the “don’t knows but will be voting” in accordance with what they said they did at the last election.
Normally this only shifts the numbers by a little bit. In this latest poll the change was quite marked.
I’ve no problems with the methodology but it is just the scale of the change this month that I’m highlighting.