By Nicholas Bennett, a former Conservative MP who is seeking re-election to Bromley Council tomorrow
A tradition in the past 25 or so years has been the exit poll announced on the main TV channels as soon as the polls close. In the main, the polls have been reasonably accurate - although in 1992 they came badly unstuck, predicting a Kinnock victory whilst the reality was a Conservative overall majority of 21.
In 2004 the US networks called a win for John Kerry but it was George Bush who ended the night re-elected as President.
This time the pollsters have to contend with the fact that in some constituencies almost half the electorate will have been eligible to vote by post before May 6th. Across the UK around 1 in 6 voters are thought to have applied for postal votes and on previous polling at least 80% will be cast compared with a probable 70% turnout overall.
The key question therefore must be: how accurate will the exit polls be?
Are Conservative voters more inclined to apply for and use postal votes? The evidence of the Bromley and Chislehurst by-election in June 2006 pointed to a Lib Dem win in votes cast in person but a win for Conservative Bob Neill as a result of the postal vote.
Will the Lib Dem surge in the first week, immediately before the postal votes were issued, be higher than those cast on Thursday when the opinion polls suggest that the Lib Dem vote has fallen back?
No doubt pollsters will try to factor in the impact of the postal vote, but, in the words of Former US Defence Secretary Donald Rumsfeld:
“There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know.”
