Do pollsters and pundits actually understand how British elections work? I sometimes wonder. Take, for instance, the debate concerning whether or not supporting gay marriage might win the Conservative party more votes than it loses. The Prime Minister says there are polls that suggest it would. Not so fast, retorts ComRes’s Andrew Hawkins. He argues:

Your letter of 19 October 2012 to The Rt Hon Cheryl Gillan MP states that “a recent poll by ComRes found that 10 percent of current Conservative voters say that the policy [to legalise same-sex marriage] would make them ‘less likely to vote Conservative’ compared with 7 percent saying it would make them ‘more likely to vote Conservative’.

I should like to put the record straight because the wrong figures have been quoted. Your figures relate to whether current Conservative voters are more likely to vote Labour, not Conservative, as a result of the policy. The correct figures are that 19 percent (of current Conservative voters) are more likely to vote Conservative, while 11 percent are less likely to do so.’

However, this is to miss the more important point from the poll which shows both that the party loses more votes than it gains as a result of the policy, and that former Conservative voters are especially less likely to return to the fold.’

Well, maybe. The Prime Minister may be guilty of being too partial in the figures he cites but it does not follow that Mr Hawkins is correct either. Anthony Wells explains why:

Polls asking if supporting gay marriage would make you more or less likely to vote Conservative show marginally more people saying less likely than more likely, but there are good reasons to be very cautious about questions asked in this format. People are not good at reporting what actually drives their voting behaviour. There is also the effect on the wider image of the Conservative party, whether it is seen as tolerant and in touch with modern Britain, which effects voters but is harder to pick up in polls, not to mention perceptions of Cameron and his leadership (as Lord Ashcroft wrote here, if Cameron did change his mind it wouldn’t just be the policy effect, but whether he would look weak, or like he was flip-flopping). I would be extremely, extremely cautious about drawing any conclusions about whether the net benefit of backing a policy is positive or negative.

I think that’s a more than plausible argument. Even so, the real argument is not whether supporting gay marriage might help the Tories win more votes overall but, much more importantly, whether it might help the party win votes where they need to win more votes.

Not all votes are equal. Some are more valuable than others. It little profits the Tories to rack up ever-larger majorities in the shires at the expense of losing seats in metropolitan areas. Granted, it can be difficult to measure the political effect of individual policies and even trickier to weigh this kind of Shire vs City trade-off. Nevertheless this is what the argument is really about.

One problem the Tories have is that their vote is not always distributed terribly efficiently. Scotland offers an extreme example of this: in 2010 the Tories won 412,000 votes north of the Tweed but their vote was so dispersed that they only took one seat. By contrast the Liberal Democrats had 465,000 votes and took 11 seats while the SNP’s 491,000 votes brought a haul of six MPs.

Now gay marriage isn’t going to transform the Tories’ tartan fortunes but it might well – at least this is the intuitive argument – assist them in other places they need to do better. Like London and other major cities.

The Tories won just 28 of the 73 seats available in the imperial capital and they fared even worse in other metropolitan areas such as Birmingham and Manchester. The Conservatives cannot do very much better in eastern England or the south-east than they did at the last election. They won 127 of the 142 constituencies in these regions and must be closer to their “ceiling” here than they are in other parts of the country.

So simply adding up the number of voters who won’t vote Tory if the party supports gay marriage and comparing that to the number who say they might if the Conservatives do embrace equal marriage rights is not a very useful exercise.

Intuitively, it seems plausible to suppose that voters in London and other cities tend, on average, to be younger and more liberal (socially-speaking) than voters in the True Blue shires. Equally, they are less likely, I think, to support a party or even consider supporting a party whose views on social policy collide so vigorously with the reality of their own lives.

To put it bluntly, some of the Tory votes in rural areas are expendable; those in the cities are not. So gay marriage – which, again, is a signal just as much as it is an actual policy position – is about being more competitive in seats such as: Westminster North, Hammersmith, Hampstead & Kilburn, Eltham, Cheadle, Hazel Grove, Solihull, Edgbaston, Sellyoak, Northfield, Nottingham South, Gedling and so on.

Now, one should be wary of over-stating the importance of gay marriage and refrain from suggesting that supporting it will transform the Tories’ urban fortunes. Nevertheless, the idea that it might help more than it hurts in these key metropolitan marginals is not daft. And nor is the notion that smallish gains in the cities are worth some leaked votes in the Tories rural strongholds. Again, some votes are more important than others and, on this matter at least, local trends and views matter more than national figures.

Of course, you can also take the unfashionable view that supporting gay marriage is a worthwhile endeavour because it happens to be the right – and conservative – thing to do.

Tags: Britain, David Cameron, Gay Marriage, Gay Rights, Tories, UK politics