The latest information raises the prospect of a surge in tactical voting tomorrowby Peter Kellner / December 11, 2019 / Leave a comment
Not surprisingly, the second big YouGov MRP survey is attracting as much attention as the first, two weeks ago. It has reduced its headline projection of the Conservative majority from a comfortable 68 to a nervy 28. Why? In some ways the answer is less dramatic than it would seem at first sight—but in one way, of potentially huge significance.
The big picture—Conservative support nationally unchanged on 43 per cent, Labour up two points to 34 per cent, Liberal Democrats down two to 12 per cent—matches the way the polling average has moved over the same period. There was a modest shift from Lib Dem to Labour around two weeks ago; since then, the figures for each party have been stable.
One clear reason for the decline in the projected Conservative majority flows from that overall shrinking of the Tory lead from 11 to 9 per cent. If the latest national figures are plugged into a simplistic, old-fashioned uniform swing model—in which the movement in party support since 2017 is assumed to be identical in every constituency, regardless of the differences between north and south, Leave areas and Remain areas, prosperous and struggling constituencies and so on—the projected result would be: Conservative 345 MPs, Labour 224, SNP 41, Lib Dem 18. This compares with YouGov’s detailed seat-by-seat projection: Con 339, Lab 231, Lib Dem 15, SNP 41. The small differences are well within the margin of error of any system of converting votes to seats.
It was a similar story last time. YouGov’s MRP projections in 2017 captured attention because they projected a hung parliament, while almost all the conventional polls pointed to a comfortable Conservative victory. But the main reason was that YouGov’s MRP surveys reported a national Conservative lead of only three per cent. Any votes-to-seats calculation would have shown a hung parliament. The big numbers were driven mainly by the overall structure of YouGov’s sample, not its MRP algorithm.
However, where MRP scored a palpable hit was the way it showed how massively different seats were behaving. A uniform swing calculation would have got the overall result right, while getting dozens of individual constituencies hopelessly wrong. YouGov’s MRP did far batter at identifying different trends below national level—correctly showing Labour ahead in Canterbury and Kensington,…