This will almost undoubtedly prove to be the most polled election campaign ever. After all, YouGov in particular have been polling almost every day throughout the course of the last five years, and they are not suddenly going to stop doing so now. There are nine other companies who are also all polling on a regular basis. Meanwhile the apparent closeness of the election race will encourage newspapers to spend as much money as they can on their own exclusive polls in the hope of being the news organisation that first breaks the news that the deadlock has finally been broken (if it ever is).

But polling is far from being a straightforward enterprise. Those who undertake polls are attempting to provide an accurate measure of the nation’s political pulse at a time when people have busier lives than ever, when many are increasingly reluctant to answer any kind of survey, and when no less than three insurgent political parties are enjoying unprecedented levels of support. There are evidently plenty of potential pitfalls to avoid.

At the same time, it is clear that the polls have influence. In recent weeks there has been much discussion of who might be willing to do a deal with whom in the event of a hung parliament, all of it predicated on the evidence of the polls that Conservative and Labour are neck and neck and that the SNP might displace the Liberal Democrats as the third largest party in the Commons. Without this evidence the subject matter and tone of the election campaign could well have been very different indeed.

In these circumstances it is clearly important that polls are subject to critical scrutiny. We should be able to satisfy ourselves that numbers that prove to be so influential but which are collected in what would seem quite difficult circumstances are indeed as robust and reliable as can reasonably be expected.

Making this possible is the key objective of the British Polling Council (BPC). Nearly all of the companies and organisations that conduct political opinion polls in the UK are members of the Council. In joining the body they have agreed to abide by a set of rules that demand a high level of transparency about how they go about their business.
Each member is expected to post on its website a description of how it conducts its polls and how it weights or otherwise adjusts or models the raw data it collects in order to arrive at its estimates of the balance of voting intentions. At the same time the details of each poll, including full details of the question asked and detailed tabulations of how the answers given vary by people’s demographic and political characteristics should be posted within three days of the poll being published – and indeed during an election campaign ideally within 18 hours of publication. In practice most polling companies typically publish these details very shortly indeed after initial publication.

Not that this means that all polls have to be published. Anybody has the right to commission a poll from a BPC member and keep the results to themselves. But if they do not want the details of their polling to be published, they do have to keep the results to themselves. If, for example, a commissioner starts to leak results to one or more journalists (perhaps selectively) then the BPC member becomes obligated to publish full details of the polling that has been leaked. If the results of a ‘private’ poll have been put into the public domain then they should be capable of being scrutinized in exactly the same way as a poll that was originally intended for public consumption.

However, conducting a poll is a multi-stage operation. At its most basic it requires the capacity to contact and interview successfully a representative body of voters (these days typically either by telephone or via the internet), to collate the results and to weight the data to a standard demographic scheme so that it has, for example, the correct proportion of men and women younger and older people etc. But it also requires an ability to identify a suitable sample design, to craft suitable questions and to undertake more complex weighting and filtering of the data than simply making sure it has the right proportion of men and women.

Not all of these stages are necessarily conducted by the same organisation. In particular a polling company (or indeed other organisation such as a university or a government department) may not have the capacity to undertake the fieldwork for a poll and thus opts to sub-contract it to a polling company that does. The job of the sub-contractor is simply to conduct the interviews and tabulate the results according to the specification of the contractor. In these circumstances the BPC decided some time ago that the body that should be regarded as responsible for the poll is the company or organisation that designed and commissioned the fieldwork, not the firm that did the interviewing.

This issue of who is regarded as responsible for a poll has arisen on a couple of occasions recently. One of the most active pollsters in recent years has, of course, been Lord Ashcroft, operating under the banner ‘Lord Ashcroft Polls’. Lord Ashcroft Polls does not have the ability to conduct its own fieldwork and thus sub-contracts this part of its polling to a number of companies, many of them BPC members. However, Lord Ashcroft Polls is responsible for the design, weighting and question wording of its polls, and thus it is the body that is ultimately responsible for its results. As it happens, Lord Ashcroft Polls is not a member of the BPC (and as an organisation that does not do work for multiple clients is not eligible to be a member), but as it happens it publishes full details of its polls in much the same way as a BPC member would be expected to do.

At the same time the Liberal Democrat Party has been undertaking quite a lot of polling in constituencies that it currently holds, seemingly with a view to establishing in which ones they might have a chance of winning again. Here too the party has been responsible for the design, and wording of the polling and for the weighting of the data, but has sub-contracted the fieldwork to a BPC member, in this case Survation. In recent weeks the Liberal Democrats have given journalists sight of some of their data, and in so doing apparently gave the impression that the polling was Survation’s responsibility. That, however, was not the case as Survation subsequently made clear in a statement its own web site. To date the Liberal Democrats, who are not BPC members, have published full details of one of their constituency polls, though not as yet the remainder.

BPC members will be making full details of their published polls available as quickly as possible throughout the election campaign so that everyone can come to their own view as to whether they believe the results are robust and reliable or not. But inevitably members can only do so for those polls for which they are themselves responsible. If someone claims their poll was conducted by a BPC member, do please check the claim out. It may not be true.

John Curtice is President of the British Polling Council and Professor of Politics, Strathclyde University