Starting in the early hours of tomorrow morning, we shall be bombarded with analyses of the local election results. Are the gains and losses for each party above, below or on a par with expectations? Is Ed Miliband on course to become Prime Minister? Has UKIP overtaken the Liberal Democrats?
This blog will offer a few tentative projections, based on YouGov surveys since the weekend of more than 5,000 voters across Britain, including almost 2,000 in areas holding local elections; but first, some qualifications.
As far as the national picture is concerned, vote share matters more than seats gained and lost. (Seats are, of course, vital for the control of each council.) As usual two sets of national figures will be produced: by the BBC tomorrow, and by Plymouth University's election experts, Colin Rallings and Michael Thrasher, in the Sunday Times. These two sets of figures will frame most of the discussion about winners and losers.
The trouble is, constructing these national projections is no simply matter. We can't just add up the votes cast, for the elections are skewed towards the relatively prosperous, Conservative voting parts of England. No elections are being held in London or Scotland, and very few in Wales or England's big provincial cities.
In our poll, Labour enjoys an 8% lead over the Conservatives across Britain as a whole; but in the areas holding local elections, the Tories lead by 7%. Any attempt to project the raw results to Great Britain as a whole must allow for this bias.
Moreover, while Labour and the Conservatives are fielding candidates almost everywhere, UKIP and Liberal Democrat candidates are standing in roughly three-quarters of the wards. How should we allow for this? To count their support as zero where they have no candidates seems too harsh. On the other hand, to count only the wards where they stand would be too generous, for they are likely to field many of their candidates where they think they have most support. I am sure that the BBC and Messrs Rallings and Thrasher will do smart things to deal with this issue, but some element of judgement is required. There can be no certain truth; it is quite possible that, as in the past, the BBC and Rallings/Thrasher figures will not quite agree.
Bearing all this in mind, this is what we have found:
The Conservatives are ahead in raw votes when people in the areas holding local elections are asked how they intended to vote today. Labour is in second place and UKIP probably third. I say 'probably' because UKIP's lead over the Lib Dems is just two points among all those giving a voting intention, a gap well within the margin of error, but it widens to five points among those who say they are certain to vote. But, to repeat, that picture is distorted by the political bias in where the elections are being held.
Compared with when these wards were last contested in 2009, both the Conservatives and Lib Dems are down 10-12 points. Labour is up 15-16 points (from a very low base: 2009 was a torrid year for the party) and UKIP up 12-14 points.
In 2009, the Rallings/Thrasher national projected share was: Conservative 35%, Lib Dem 25%, Labour 22%, UKIP 4%. YouGov's latest local voting figures allow us to estimate the change for each party since 2009. When we apply those changes to the Rallings/Thrasher 2009 calculations, we produce a national projected vote share of: Labour 37-38%, Conservative 24 25%, UKIP 16-18%, Lib Dem 13-14%.
An alternative way to project the national vote share is to compare voting intentions not with the 2009 local elections but how people voted in the 2010 general election. When we do this comparison, our national projection becomes: Labour 35-36%, Con 24-25%, UKIP 17-19%, Lib Dem 10-11% - not vastly different, except for a wider gap between UKIP and the Lib Dems. Finally, we can adjust for the political bias of the pattern of today's contests by comparing general election voting intentions in the areas with local elections and Great Britain as a whole. This means reducing the Conservative raw-vote share by seven points and UKIP's by three; adding eight points to Labour and two to others; the Lib Dem vote share is not affected. When we do this, then our national projected vote share is: Labour 36-37%, Con 26-27%, UKIP 13-15%, Lib Dem 13 14%. Now it is too close to call between UKIP and the Lib Dems.
So, take your pick. One key finding from YouGov's surveys is that many people give different answers when asked how they intend to vote this week compared with how they would vote in a general election. So both Labour and the Tories are likely to underperform their normal poll ratings, while the Lib Dems and very possibly UKIP will do better than their conventional polling numbers suggest. That, too, should be borne in mind if the BBC and Rallings/Thrasher national vote projections show the Tories well below 30% and Labour well below 40%.
All in all, what voters do today will be important, both locally and nationally, fascinating for those of us who follow these things, and possibly dramatic. But if you are looking for simple winners and losers this weekend, stick to soccer, the Voice or Britain's Got Talent.