The latest YouGov Mayoral polling has Boris back in the lead, but within the margin of error. Guido imagines the fluctuation will continue for a while, but Joe Murphy at the Standard hits the nail on the head:

“What the headline figures do show, beyond doubt, is that Ken has failed to extend or harden his January lead. He is like a marathon runner who, in a stupendous effort, catches up with the leader only to find he cannot break ahead. “

Only 44% believe Ken will keep his promises, despite liking the ideas. As ever the breakdown is more interesting than the headline figures:

“In inner London, Ken is ahead by 53 per cent to 47. But the huge outer doughnut is sticking with Boris by 52 to 48. Among voters aged 18 to 24 the pair get 50 per cent each. Ken is somewhat ahead among 25 to 59-year-olds. But Boris has a massive “grey power” advantage, a two to one lead among the over-sixties.”

Crucially that suburban doughnut is a) bigger and b) full of those over 65s who are more likely to vote.