I should start with an apology. This blog will have a special, and possibly unhealthy, appeal for political nerds. It addresses some technical issues to do with democratic theory and the detailed arithmetic of Scottish opinion.

Throughout last year, I regarded Boris Johnson as the likeliest winner of London’s coming mayoral election. YouGov and other pollsters showed consistently that around one-in-five Labour supporters would desert Ken Livingstone and vote for Boris. Our latest poll tells a different story.

YouGov's latest poll, showing the Conservatives five points ahead, made the front page of the Sunday Times and livened up the blogosphere.

Things have not worked out as the government hoped. 12 months ago it was predicting steady economic progress. In the event, growth in 2011 was less than 1%, and the economy ended the year slipping backwards.