BMG’s latest Westminster voting intention poll, on behalf of The Independent, shows the Brexit party’s share decrease slightly, with only minor changes for other main parties.
The poll was conducted between 2nd – 5th July and surveyed 1,532 GB adults.
The Conservative party’s voting intention remained largely stable since last month, increasing by 2 percentage points to 28%. The Labour party’s voting intention is unchanged from June on 27%, leaving the two parties neck-and-neck.
The Liberal Democrats appear to be maintaining their support (18%), as are the Greens (6%).
The Brexit Party’s vote intention has dropped by 4 percentage points from last month, giving them a share of 14%. However, keep in mind that the historical record of polling shows that there is a 9 in 10 chance that the actual share lies within 4 points of the estimates provided by this poll. We should therefore be cautious to attribute a 4 percentage point change as a shift in public support for the Brexit Party.
Please note that this month we have made changes to our voting intention tracker chart. In previous months, the Other category consisted of: SNP, Plaid Cymru, The Green Party and Other parties. However, after recent increases to the Green Party’s vote intention share, we have decided to remove them from the Other category.
**A note on the format of our vote intention question**
Readers should note that, as it stands, BMG’s voting intention question is asked in two stages. Firstly, we ask respondents to select from Labour, Conservative, Liberal Democrat, SNP (if living in Scotland), Plaid Cymru (if living in Wales), or “another party”. Those respondents who select “another party” are then presented with parties who are less established or who typically attract less support. This list currently includes the Brexit Party, Change UK, the Green Party, and UKIP.
We understand why some may view this as unfair given the recent performance of the Brexit Party in the European Elections.
Our current question structure is based from our analysis of our 2017 general election polling where we overestimated the support for the Greens and UKIP. There is evidence to suggest that prompting for smaller parties, or those yet to contest General elections has led to respondents being more likely to overstate their support for these parties when compared to the election result. Indeed, it is also worth noting that most pollsters, including BMG, overestimated Brexit Party support at the recent European Elections.
As pollsters it’s important that we maintain methodological consistency where possible in order to ensure consistency for tracking purposes. Any changes should be made on the basis of evidence.
With this in mind, readers should be aware that, in an attempt to understand what the best approach should be, we have scheduled the undertaking of a randomised control trial to examine more formally the effects of our current question format.
The results of this experiment will be published on our website and inform our approach moving forward.
Had we changed the structure of the question without testing for the impact of our current structure, we would have been unable to identify whether any changes are likely the result of a genuine change in sentiment or whether the change is simply related to the format of the question and the parties which were initially prompted for.
By taking an experimental approach, we will be able to understand the degree to which, if at all, the question format is having an effect, and then comment on future changes with greater confidence, should our approach prompt any change.
However, there comes a point where parties are attracting enough support where it is both likely that they will be standing in the vast majority of seats at the next General Election and where not including them in the first list would risk understating their support.
This is a matter of discussion internally and we have scheduled survey experiments to test the effect of format over the course of the next fortnight. We will be making a decision on whether and how we change the structure of our vote intention question in advance of our next scheduled release at the beginning of August and will continually review and update our methodology if we deem necessary. Any future changes to question prompting will be outlined in full in our next release.
Methodology, fieldwork dates, and a full breakdown of these results can be found here.
Please note that our method has changed after the 2017 General Election. Full details can be found here.
For a more detailed breakdown of results from this poll, or any other results from our polling series, please get in touch by email or phone.