"Now this is just a bit of fun," Peter Snow used to say as he wielded his swingometer after each sensational byelection, to reveal the House of Commons stuffed with 500 Lib Dem MPs or whatever it was that would result if Britain as a whole voted the same way in a proper election – which, of course, this was not.
Extrapolating from the council elections to next year's general election is not quite such a silly exercise, seeing as large parts of the country were voting at once, and the real concerns that people have with their town halls mean a protest vote is not quite the same free hit that it can be in a parliamentary byelection.
Projecting general election results from local election polls is fraught because an expected 36% turnout is little more than half what is likely next year, and that is only within that (mostly urban, and exclusively English) half of Britain that has a council vote.
The European ballot boxes, opened on Sunday night, are a sounder basis for projection in the sense that the whole of the UK had MEPs to elect, but seeing as the Euro-parliament is so remote and poorly understood, these elections have been heavily prone to protest voting, from the great Green surge of 1989 onwards, which disappears by the time of the real contest.
Sky News calculations using the share of vote so far project a House of Commons with Labour on 322 seats, which is 64 up on 2010 and just four short of the 326 required for a working majority. The Tories would drop back 45 to 261, very close to Labour's 258 last time around, suggesting that a general election today would produce something of a mirror image of the one that took place four years ago.
There would be a bigger difference for the Lib Dems, who would shed 20 MPs, more than a third of their total, being reduced to 37. From Berwick to Birmingham and on to Bude (in North Cornwall), Nick Clegg's party would suffer defeats on this sort of a result, if the swing were uniform. But then the patchy nature of the town hall results strongly suggests the swing would not be uniform, making it hard to make confident projections of a loss in anything but the most marginal seat.
The most striking feature of the forecast of all, however, concerns the minor parties. The assorted parliamentary "others" would come back with just 30 seats, only one more than last time, a reminder that despite the great slice of the electorate that Ukip appealed to, the voting system for the Commons – which requires parties to concentrate enough votes to come out ahead in particular locations – still represents a formidable obstacle in the way of insurgent parties seeking to break the mould.
The psephologist Rob Ford, of Manchester University, says: "We know that people vote differently in local and national elections, so you have to be careful. But we can get some sense of the relative standing of the parties based on real votes, which is always interesting."
In particular, Ford – who has co-authored a new book on Ukip – believes that the geography of the council results can tell us something about the battleground for 2015. "There is an increasingly stark contrast between diverse metropolitan England and particularly London on the one hand", he says, "and what we might call 'middle England' small towns on the other. Labour is shoring up well big cities, but is – just like the Tories – being squeezed by Ukip elsewhere."
For 2015, Ford believes, this suggests there are at least large parts of the country where Ukip's strength in voting for councils could play an important role in 2015.
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