In an interesting article in The Times (which Skipper brought to my attention) Peter Riddell sets out some simple rules for interpreting opinion polls (and advises against over-interpretation). The rules (slightly adapted) are:
Ø Always look for levels of support not leads, which exaggerate differences.
Ø Disregard variations of one or two points, which are within the margin of error.
Ø Compare the results of individual polls from the same polling organisations not different ones (because they use different methodologies).
Ø Look at the underlying trends.
This is good advice (although it is also a good idea to look at whether the same underlying trend is corroborated by other polling organisations).
The latest YouGov poll puts the Conservatives on 39%, Labour on 32%, and the Liberal-Democrats on 16%. Following Riddell’s rules, and comparing this with previous YouGov polls, the underlying trend shows a dip in the level of Labour support and a rise in the level of Conservative support since the end of last year (At the end of September, YouGov had Labour and the Conservatives on level pegging on 36%. This was probably a "conference bounce". This aside YouGov has had the Conservatives in the lead since the end of April). ICM, Populus and BPIX have also had the Conservatives in the lead since the end of April/May. So has MORI, apart from two recent polls giving Labour a small lead. The level of support for the Conservatives has been in the 35-38 range, occasionally peaking at 39-40%. Labour's support has been in the 31-35% range, occasionally peaking at 36-37%. There are no doubt a number of reasons for Labour's relatively poor showing but Iraq, the Labour “succession crisis”, the “Cameron effect”, together with the inevitable disappointments and travails which go with being in office for 10 years, seem to me to be the most obvious factors. However, in a comment on Anthony Wells latest post on UK Polling Report (which is the best source I have found for informed comment on polling trends: see Links) Andy Stidwell makes the following observation:
“Although the Conservatives are beginning to register solid leads in the polls, such as this YouGov survey, their share of the vote is still rather low.
In fact, looking at the last 73 opinion polls on this website, not a single one has any party reaching 42% of the vote, and only 9 of them have any party reaching 40%, (8 Conservative and 1 Labour).
It will be interesting to see if this pattern continues in 2007, or whether David Cameron can push the Tories towards 45%”
Given that the electoral system currently disadvantages the Conservatives the latest YouGov ratings would leave them as the largest party but (just) short of an overall majority in the Commons.
Of course, there won’t be an election for some time and things could change; but if I was a Labour MP in a marginal constituency I would be less worried about “Blair’s legacy” than my own future.