YouGov have some more AV polling, this time for Channel 4. In the past the assumption has been that AV would help Labour and the Liberal Democrats, and indeed this was backed up by polling evidence from past elections. In their final poll before the 2010 election YouGov asked respondents how they would have cast their second preference votes if they had been voting under AV.
Amongst Conservatives voters 45% would have given their second preferences to the Lib Dems, 5% for Labour, with the rest not sure, not casting a second vote, or casting one for minor parties. Amongst Labour voters, 6% would have given their second preference to the Conservatives, 64% to the Lib Dems. Lib Dem voters would have split their second preferences in favour of Labour by 42% to 27% for the Tories. Peter Kellner’s estimate based on those splits is that this would have cost the Conservatives about 30 seats, with Labour gaining 11 and the Lib Dems 19.
However, AV does not by definition help Labour and hurt the Tories. If Lib Dem voters split in favour of the Tories, and Labour voters were less willing to transfer their support to the Lib Dems there would be a different result.
YouGov repeated the same experience at the end of June. Second preferences now break differently. Conservative voters are much the same, but Labour voters are now much less likely to transfer to the Lib Dems, from 62% at the election, now only 33% of Labour voters would give their second preference to the Lib Dems. Lib Dems now break in favour of the Conservatives rather than Labour, though not by very much (38% to 33%).
None of this should come as a surprise of course – Labour voters are obviously less likely to give second preferences to the Lib Dems if they see them as Conservative-allies, and those Lib Dem voters who preferred Labour over the Tories at the election may no longer have the Lib Dems as their first preference in the first place! The impact, however, is that vote transfers from AV would now help the Conservatives more than Labour. Peter’s calculation is that had these transfers applied in the general election (admittedly a rather false scenario!), the Conservatives would have lost only 2 seats, while Labour would have lost 13.
Precisely predicting how AV votes and transfers will translate into seats is a complicated matter (though one we’ll have to tackle should the AV referendum be successful), but the point is that the assumption it is damaging to the Conservatives is based on Labour and Lib Dem supporters disproportionately swapping their second preferences between one another. If that changes, as the polling suggests, and Conservative and Lib Dem supporters instead tend to second preference each other’s party, AV would end up disproportionately hurting Labour.