Why AV won't necessarily help Labour anymore
Over on Left Foot Forward there is a paper by a Dr Matt Qvortrup arguing that the introduction of AV would help Labour and hurt the Conservatives, and therefore it would be in the Labour party's partisan interest to support it.
The paper is almost all made up of polling evidence from elections between 1997 and 2010 which demonstrate that the Labour party would have gained more seats under AV (or at least, lost out less than the Tories!), and reference to the 2008 London mayoral election where Labour performed better under AV (Ken Livingstone still lost, but the re-allocated second preferences split in his favour, so AV was a plus for Labour)*
I wouldn't make any argument with any of this, throughout this period AV would certainly have helped the Liberal Democrats and been kinder to Labour than to the Conservatives.
Where I would depart from the argument is the assumption that the same pattern would apply now. Normally, in the absence of other information it is a fair assumption that people will keep on doing what they have done in the past. In this case though, there has been a massive shift in British politics and it is fair to question whether that assumption is safe.
AV voting would have helped Labour between 1997 and 2010 because Labour voters were likely to give second preferences to the Lib Dems and vice-versa. To put it simplisticly the left-of-centre, anti-Conservative vote was split between two-parties, and AV would have effectively united that vote behind the better performing of the two parties in each seat.
The formation of the coalition will likely have changed that. People who voted Liberal Democrat seeing it as a left-of-centre, anti-Conservative party probably aren't voting Lib Dem anymore. The rump of remaining Liberal Democrat supporters are likely to be more positively inclined to the Conservatives, and Conservative supporters themselves will likely see the Lib Dems more positively.
In his paper Dr Qvortrup acknowledges this with reference to an article by John Curtice floating the same possibilities, but handwaves it away by saying there is no evidence of it and Curtice is just making assumptions. As Carl Sagan once said, "absence of evidence is not evidence of absence".
As it happens, while John Curtice didn't cite it, there is evidence to back up Curtice's assumptions. YouGov asked a "how would you vote under AV?" question at the time of the general election and found a similar pattern of second preference distribution as everyone else - Labour voters were more likely than
Conservative voters to give second preferences to the Lib Dems, and Lib Dem second preferences broke in favour of the Labour party. However, YouGov then repeated the exercise in July 2010 after the formation of the coalition to test the hypothesis that pattern of second preferences would have shifted.
Indeed it had - Conservative voters had become more likely to give second preferences to the Liberal Democrats, Labour voters much less likely to give second preferences to the Lib Dems, and Lib Dem voters' second preferences now split evenly between Labour and the Conservatives.
On a crude projection, these splits would still been slightly better for Labour than the Conservatives, but the more important finding was the change in the pattern of second preferences. That evidence comes from July 2010 when the Lib Dems were still in the high teens - my guess is that these trends would be even more pronounced
now as the Lib Dems are ever more reduced to a rump of those supporters happy with the Conservative coalitions and Labour supporters become ever more antagonistic towards the Liberal Democrats.
Of course, that is still an assumption. While there are no more recent polls that specifically asked about second preferences under AV, we can at least look at what Liberal Democrat voters say in other questions that might act as a proxy for whether they prefer Labour or the Conservatives. Looking at the most recent YouGov polling this week:
Remaining Lib Dem voters think David Cameron would make a better PM than Ed Miliband by 31% to 1%. Remaining Lib Dem voters would prefer a Conservative led government to a Labour led one by 60% to 26% Remaining Lib Dem voters approval rating of Cameron is plus 44, of Miliband minus 31.
The assumption that these voters would still be more likely to give their second preferences to Labour than the Conservatives is, quite frankly, fanciful.
Of course, the main reason for this shift isn't that Lib Dem voters have suddenly become more right-wing or more pro-Conservative. They haven't - the opinions of people who voted Lib Dem in 2010 are still tilted towards Labour.
The reason is that most Liberal Democrat supporters from 2010 don't support them anymore! Many or most of those Liberal Democrat voters who in May 2010 would have told pollsters that their second preferences would go to Labour would now give their first preferences to Labour. Those that remain are a more pro-Conservative rump.
And there, as they say, is the rub. AV is not a system that automatically favours right wing parties or left wing parties, nor one that will always favour Labour or always favour the Conservatives. It depends entirely upon the circumstances - during recent decades it will have tended to have been better for the left because we've had a political landscape where there were two left-of-centre parties with supporters who were comparatively comfortable with voting tactically or lending their votes to each other.
If at the next election the landscape is instead a Lib Dem party whose support has been reduced to mainly those voters who are reasonably well disposed to the Conservatives, where many Conservatives view the Lib Dems as allies rather than enemies, and where many Labour voters see the Lib Dems as turncoats and Tory stooges, the pattern of second preference voting may be utterly different.
(*As an aside, I'm confused by the rather odd claim that Ken Livingstone would have won the London mayoralty had he secured an extra 11,182 votes. After second preferences had been re-allocated Boris Johnson won the election by 1,167,738 votes to Ken's 1,028,966, a majority of 139,772.)
