Leaked Populus poll on how opposing Brexit would impact Labour support
The Guardian today has the results of a Populus poll for Best for Britain, apparently leaked without their permission. It found "almost a third" of respondents who would less likely to vote Labour if the party was committed to stopping Brexit, compared to 25% who said it would make them more likely - presumably the opposite of the headline finding the client was hoping for.
As regular readers will know, I think "would policy X make you more likely to vote Y" questions are of little or no worth anyway. Many respondents use them to indicate their support or opposition to the policy in question, regardless of whether it would actually change their vote, and you typically find a substantial proportion of people who say it would make them more likely to vote for a party already do so (and many of those saying less likely would never do so anyway).
This means the response from Best for Britain in the Guardian write up about the picture being skewed by Conservative and UKIP voters, while it may sound like special pleading, is probably quite right. I expect the third of people saying they'd the less likely to vote Labour are indeed probably largely Conservative and UKIP voters who wouldn't vote Labour anyway. On the other hand, the people saying more likely are probably largely Labour voters who are already voting Labour - it's why it is such a poor approach to the question.
In the meantime, it's a reminder of why one needs to be a little cautious about polls commissioned by campaigns. You can never tell what other polls they did that they never released. It is the job of pollsters to make sure the actual questions are fair and balanced, but ultimately it's often up to clients whether they keep a poll private, or stick it in a press release.
