In the past, it was often assumed that the Alternative Vote (AV) would benefit Labour, as the party could bank on large numbers of second-preference votes from Lib Dem supporters.
One simulation by the Electoral Reform Society suggests that, had the last election been held under AV, Labour would have gained four seats, the Tories would have lost 25 and the Lib Dems would have gained 22. In 1997, thanks to anti-Tory tactical voting, Labour's majority would have swelled from 179 to 245. In 2005, it would have been 88 rather than 66.
But a new Channel 4/YouGov poll suggests that it's now the Tories, not Labour, who would gain most (or lose least) from AV.
As the table below shows, before the election Lib Dems voters would have split their second preferences in favour of Labour rather than the Tories (42 per cent to 27 per cent). Returning the compliment, 64 per cent of Labour voters would have put the Lib Dems as their second preference.
YouGov's estimate based on those splits is that this would have cost the Conservatives roughly 30 seats, with Labour gaining 11 and the Lib Dems 19.
But in this era of "new politics" that's all changed. By a slight majority (see table below), Lib Dem voters now split in favour of the Tories (38 per cent) rather than Labour (33 per cent), while only 33 per cent of Labour supporters would back the Lib Dems.
The upshot of all this is that vote transfers from AV would now benefit the Tories more than Labour. If repeated at a general election, the transfers would have cost Labour 15 seats but the Tories would have lost just two. The Lib Dems would have gained 15 seats.
I'd expect these figures to strengthen the cause of those on the right (such as Philip Blond) who argue that the Tories have nothing to fear from AV. They should also increase the likelihood of a Tory-Lib Dem pact at the next election.
Meanwhile, in Labour, diehard tribalists such as John Prescott and Andy Burnham (electoral reform is of interest to "Guardian readers" only, apparently) will seize on the figures as evidence that the party should avoid the Alternative Vote at all costs.
But the lesson they should draw from this survey is quite a different one. If Labour wants to enter government after the next election, it will need Lib Dem support, be it from tactical voting or second-preference votes.
Figures like Prescott (a man who represents all that is wrong with Labourism) should drop the hectoring, condescending tone they use towards the Lib Dems and make a more constructive and sophisticated appeal to the party's supporters. As the data shows, hurling abuse at the Lib Dems isn't going to win Labour any votes.