Communicate Research’s latest poll for the Independent has topline voting intention figures (with changes from last month) of CON 34% (-2) LAB 29% (-8) LDEM 21% (+8), a huge reduction in Labour support and surge in the Lib Dem rating.

While ICM and YouGov too have shown increases in the Lib Dem vote this month, I suspect the contrast with Communicate’s last poll is more a result of their methodology. Like MORI Communicate do not perform any political weighting of their samples, which results in far more volatile figures. Political weighting is rejected by some pollsters because of the problems of false recall – it is well known from call back and panel studies that people do not accurately report how they actually voted at the last election, so when pollsters weight according to past vote they need to take this into account and weight to shares of 2005 vote that are adjusted to take account of their estimates for false recall. Phone polls that are not politically weighted tend to be slightly more favourable to Labour, but more importantly tend to be more volatile – differences from one month to the next may be down to there simply being more or less Labour supporters amongst that month’s sample.

There was also a slight change to Communicate’s research this month. The way the question is worded is altered slightly and there is an extra adjustment for the “spiral of silence” – people who say don’t know or refuse to answer even Communicate’s squeeze question are re-allocated based upon their party ID. This month the adjustment seems to have slighted favoured the Conservative party.

ICM have also released their latest poll on voting intentions in Scotland. The topline figures, with changes from their last Scottish poll are, in the constituency section – CON 13% (nc), LAB 31%(+2), LDEM 17% (nc), SNP 33% (-1) and, in the regional vote, CON 14%(+2), LAB 27%(+1), LDEM 17%(-2), SNP 33%(+2), GRN 5%(-1)

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