Warning: this post is about election mechanics and likely to be of interest only to political anoraks.
But if you have an interest in politics, there have been two posts at Political Betting
this week that you absolutely have to read.
Not all that long ago, the most insightful views on politics came from politicians, jounalists or academics and were first launched in lectures or newspaper/magazine articles.
I'm starting to find that a lot of cutting edge thought is coming through on blogs, and Political Betting
is one of the best.
It is received wisdom among a lot of journalists and academics that David Cameron needs a lead of ten or eleven percentage points in vote share to win a parliamentary majority because of an inbuilt bias in the electoral system. (And I wonder how the people who write and post gleefully about this would feel if the bias were the other way round.)
Blogger Andy Cooke has written two seminal articles on pb.com making a well-argued strong case that this receieved wisdom may at best significantly overstate the bias in the system and at worst be completely wrong.
His first article, Does Cameron really need an 11 point lead?
examines and explains several key factors which enabled Tony Blair to win landslide majorities in the 1997 and 2001 elections, and a working majority in 2005, with far fewer votes than were cast for John Major in 1992.
He highlights differential turnout in safe Labour seats, anti-Tory tactical voting, and Labour's strong performance under Tony Blair in key marginals.
However Cooke also points out that all of these factors are likely to be strongest in their impact when Labour are doing well but have the potential to unravel if their support declines.
Andy Cooke's second article, Could Cameron get a majority with a lead of just 5 points?
looks at how each of these factors could unravel, increasing the impact of a swing from Labour to the Conservatives.
For example, anti-tory tactical voting which had a marked effect in 1997 and 2001 was obviously far less significant in 2005, and this certainly contributed to the Conservatives regaining several seats which I know well. In the coming election there is a good chance that anti-tory tactical voting will be weaker still while anti-labour tactical voting may have more of an effect.
If Andy Cooke's assumptions are correct, a 7% voting share lead for DC would produce a working Conservative majority, a 6% lead would give him a good chance, and a 5% lead a slight possibility of a Conservative majority.
There is considerable scope for argument about whether Andy Cooke's assumptions are correct, but his arguments look reasonable and his conclusions look a lot more plausible than those who argue that David Cameron could get 40% of the vote against 30% for Gordon Brown and still fail to get a majority.