This week’s YouGov/Sunday Times polls is now online here. Topline voting intention figures are CON 29%, LAB 40%, LDEM 9%, UKIP 14%. The eleven point Labour lead is at the high end of YouGov’s recent results so could be a sign of the infighting over Europe reversing the recent picture of narrowing Labour leads… or could equally well just be normal variation within the standard margin of error.

Last night I grumbled about the problems with polls purporting to show what issues affect people’s voting intentions. YouGov have asked it in a way that gets round one of those problems, that of giving a single issue false prominence, by asking people to pick from a list of all sorts of issues. Same-sex marriage remains an issue that only a small minority (7%) pick out as one that will affect their vote, and by 58% to 42% those people say they would be more likely to vote for a party that supported gay marriage. More people, 28%, say that Europe is one of the three or four issues they think would affect their vote at the next election, with most of them saying they would be more likely to vote for a party that promised a referendum.

Even asked this way strong caveats still apply – people still are not very good at understanding the motivations of their own decisions, and people still really don’t vote on individual policies or policy areas. They vote on broad perceptions of party, of competence and of the leaders. Individual issues play into those perceptions of course (does this party consider the same issues to be important as I do? Do they have similar values and beliefs?) but so do things like strength and weakness, competence, unity and so on.

It also gives the opportunity to point out something else that, while I think is beginning to get through to the commentariat and politicians, still needs to be repeated whenever possible. Only 49% of UKIP voters named the issue of Europe. In other words, 51% of UKIP voters don’t even consider Europe to be in the top three or four issues that affect their decision. The simplistic view that UKIP support is all about Europe and, by extension, it is policies on Europe that will suddenly win back UKIP voter is just that – simplistic.

Moving on to those wider perceptions of how the Conservative party is seen, only 10% of people now see the party as united, 73% divided. YouGov have been asking the same question since 2003 and this is highest proportion so far seeing the Tories divided, more than under Iain Duncan Smith. The party is not seen as widely divided as Labour was towards the end of Tony Blair’s leadership (6% united) or under Gordon Brown (just 3% united at its worse), but it is certainly in that sort of territory. Also note, however, that while perceptions of division are widely seen as negative they are not necessarily fatal – in 2004 over 60% of people saw Labour as divided but they still won the 2005 election. Personally I think there is some truth in the idea that division drives away voters (constant infighting makes a government look incompetent, and we know perceptions of competence are a key driver of voting intention), but its not as simple as division equals defeat.

A majority (54%) of people continue to support the introduction of gay marriage. Asked if the subject should be decided by a referendum or by Parliament it only narrowly follows my past comment that people support a referendum on absolutely anything you ask about – just 39% think there should be a referendum on gay marrige, compared to 34% who think it should be left to Parliament.

On Europe, referendum voting intention asked using the wording in the Conservative party’s draft bill has 36% of people saying they would vote YES (to stay), 45% saying they would vote NO (to leave). Asked about the Conservative rebellion over the Queens speech people are pretty much evenly split on whether they are more sympathetic towards David Cameron or Conservative MPs (most are sympathetic towards neither!). Conservative voters are far more on David Cameron’s side – 52% are more sympathetic towards Cameron, 19% his rebellious MPs.

Regular readers will know that I have often complained about surveys claiming to show that an issue or policy stance will make people more or less likely to vote for a party. I’ve written about it previously here, here and here.

Polls like this are very popular with pressure groups and political campaigns because they inevitably end up suggesting that the issue they are campaigning on is really important and will swing votes, and MPs better listen to them and do what they say or they’ll lose their jobs. The problem is people don’t actually behave like that – we know from academic studies that people don’t vote on single issues, they vote on broad things like party identification, perceptions of party leaders, perceptions of competence, economic trust, party image and so on. Individual policy stances play into these things, but to reduce the complex drivers of voting behaviour to polling questions purporting to show that “If party X follows policy Y then 14% of people won’t vote for them” is simplistic and naive.

I won’t recite at length why these questions give such misleading data, but there are a number of reasons. Firstly respondents use them to indicate support or opposition to a policy or a party regardless of whether it would actually change their vote. Secondly it gives false prominence to a single issue, when in a real election campaign that issue would be considered alongside other important issues like the economy, leadership perceptions, party competence and so on. Thirdly people simply aren’t very good judges of what drives their own decision making. Working together these produce results that overestimate the impact of single issues on voting intention.

Yet, it is a question that people eternally want asking – and keeps provoking rather silly news stories, full of hyperbole about gay marriage dooming the Conservative party. Hence it is worth trying to do it sensibly.

In the Sunday Times/YouGov poll this week they first they asked what three or four issues would be most important to people in deciding their vote at the next general election. It’s still simplistic of course, and still depends on people understanding the drivers of their own voting intentions when they don’t, but at least it doesn’t give an issue false prominence.

Asked this way, 56% say the economy will be an important issue in how they vote, 42% immigration, 36% health, 28% unemployment and so on down to gay marriage, of which 7% of people say it will be an important issue in deciding their vote. This includes 5% of current Tory voters and 5% of 2010 Tory voters.

Of course, not all these people who care about the issue are necessarily opposed to it. YouGov asked those 7% who said gay marriage was likely to be an important factor in deciding how they voted whether it would make them more or less likely to vote for a party – 54% said more likely, 44% less likely. In other words three and a bit percent of voters claim they are more likely to vote for a party that supports gay marriage, three and a bit percent claim they are less likely.

Looking just at Tory voters, that 5% of Tory voters who say it will be an important issue in deciding their vote are mostly people who would be less likely to vote for a party that supported it… but this still equates to just 4% of Tory voters – that is, about 1 percentage point of their current 34 percentage points of support. Hardly a huge election winning or losing issue.

Even this is likely to be an overestimate of course, because as I said at the start of the post, people aren’t very good judges of what drives their voting intention and individual issues aren’t actually much of a driver of voting intention; party identification, competence, the economy, leadership perceptions are the sorts of things that actually drive votes. On top of that, gay marriage is very high up the news agenda right now – I expect it will be a far less high profile issue in 2 years time. It also ignores whatever positive impact the issue might have.

In terms of a direct effect, my guess is that, by the time of the next election, gay marriage will have negligible impact on Tory support. Potentially more important is the indirect effect – whether, on one hand, that it adds to perceptions amongst traditionalist voters that David Cameron does not understand or reflect their views or, on the other hand, helps build perceptions that the Conservatives are a more modern and tolerant party that is at ease with the modern world.

Things like this are almost impossible to measure in polls, but are probably far more important. My own view is that Michael Ashcroft is right on this – in terms of impact on party perception Cameron may or may not have been right to come down the route of pushing gay marriage, but now he is here he must continue. Changing his mind won’t convince his detractors that he actually agrees with them, it will just make him look weak, while fatally undermining whatever positive impact it has on making the Conservative party look more tolerant and in tune with modern Britain (that said, I’m far from convinced that it is having a positive impact on that front, because the impact of David Cameron supporting gay marriage risks being cancelled out by the impact of right-wing Conservative backbenchers opposing it).

Meanwhile YouGov’s weekly poll for the Sunday Times has topline figures of CON 34%, LAB 41%, LD 12%, UKIP 8%. The mid-week Sun polls clearly suggested the referendum boost was on the wane, but these figures suggest it hasn’t completely gone yet.

I return once again, with a heavy heart, to the issue of gay marriage. There is more rather one-eyed polling by the campaign against gay marriage, dutifully reported the Telegraph. The way polling commissioned by the lobby opposed to gay marriage is reported by the newspapers and those commissioning it is almost a masterclass in poor interpretation of polls.

Firstly we have the problems of polls conducting using agree/disagree statements, which risk bias in the direction of the statement asked (which I have written about at length here) and often give contradictory answers if properly balanced with statements in the other direction. For example, in this poll 62% of people agreed with the statement “marriage should continue to be definied as a life-long exclusive commitment between a man and a woman”. The campaign against gay marriage have consistently focused on this question and interpreted this as meaning that 62% of people are opposed to gay marriage. However, the same poll found people agreeing by 44% to 38% that “legalising gay marriage is important because maintaining the distinction between civil partnerships and marriage worsens public attitudes towards gay people”. One could just as easily cherry pick that question from the poll and claim that more people support than oppose gay marriage.

As I have written before, we have a multitude of polls that have actually asked directly whether or not people support the legalisation of gay marriage, and they should really be the starting point for anyone looking for polling evidence of whether people support or oppose gay marriage. I summarised the main polling on the issue earlier this month, but suffice to say, polling asking a straightforward question on whether people support or oppose gay marriage consistently finds more people support it than oppose it. Polls that offer more nuanced options, and ask if people support gay marriage, only civil partnerships, or neither gay marriage nor civil parterships, still consistently find support for gay marriage in the mid-40s, but normally find a substantial minority of people who support civil partnerships but not gay marriage, so sometimes show more people opposed to gay marriage than support it.

Secondly we have “would X make you more or less likely to vote for party Y” questions. Again, I have ranted about these at length before, but essentially it is a type of polling question which gives false prominence to and therefore greatly overstates the importance of specific policies when voting intention is actually driven by broad perceptions of parties, their competence, leaders, capability on major issues like the economy and so on.

Now we have that hoary old chestnut of a poll showing people want a referendum on gay marriage. As previously discussed, if asked in an opinion poll people want a referendum on almost everything – unsurprisingly, given that questions on referendums basically boil down to “would you like to have a say on this or should it be left to the hated politicians to decide”. It doesn’t mean there is some huge untapped demand for a referendum on that particular issue, people support a referendum on anything you ask about (the one exception I have managed to track down was a MORI poll back in 2001 that found people did not want a referendum on abolishing the monarchy)

Why do I keep coming back to this? I think its mostly the consistently credulous and one-sided reporting of polls on gay marriage in some sections of the press. Readers of some newspapers could be forgiven for thinking that the polling showed that the public were opposed to gay marriage, when any fair minded look at the broad range of polling on the issue would show that the balance of opinion is broadly positive towards it.