Why the tide is turning against Ken Livingstone

Could this go down as the week that Ken Livingstone lost the mayoral election? The results of today's YouGov poll are striking, with Tory challenger Boris Johnson still 10 points ahead. Of course, it is just one poll - and polls can be wrong. But something else in the air this week suggests Londoners are preparing for a change of mayor. Power and credibility are starting to flow in Boris's direction in a way many - even in his own party - would not have believed possible a few months ago. That presents Ken with a very tough challenge indeed.

For a start, this poll suggests London is now seriously thinking about ejecting Livingstone from City Hall. Although Johnson's lead in "first preference" votes is down from 12 per cent to 10 per cent, there is no evidence of any major shift of opinion back to the Labour candidate. Moreover, the results will be deeply disappointing for the Liberal Democrat, Brian Paddick: far from his campaign achieving lift-off at this crucial point, he has dropped back two points.

The poll also suggests that Paddick's second-preference votes may be shifting from Johnson to Livingstone: Boris's lead over Ken among Paddick second preferences has dropped from seven to two per cent. Yet Johnson is still in the lead overall on second preferences.

Is this poll accurate? When a previous YouGov poll first showed Johnson ahead, Labour rushed out its own, slightly earlier, MORI polling which showed Ken still narrowly in the lead. Revealingly, Labour has not since published any further polling evidence to contradict the YouGov polls showing Boris ahead.

There is some good news for Ken. When Londoners are asked which candidate would best deal with a terrorist attack or which would be best placed to improve the lives of minority ethnic communities, the Mayor is seen as out-performing Johnson.

Yet these are not the things on which London voters say they will judge the mayoral hopefuls. Their top priority is "crime and safety" followed by "public transport". The poll shows a broadly even split on whether or not people think travel in the capital has got easier in the past four years. Perhaps more serious, a significant proportion do not believe crime has fallen in their area, although official statistics suggest it has.

In other words, for all Ken's efforts, people do not appear to feel he has made much difference to their lives. That being the case, London's voters appear ready to evict him in favour of the other side. Put another way, Ken's main problem is longevity, being in City Hall for eight years. Unlike the Daley family's Chicago, the London electorate is unlikely to want to keep the same mayor for 10 or 20 years.

Yet Ken's wider problem is that it is increasingly accepted in Whitehall, the boroughs and the media that a change of mayor is now a real possibility. Few apart from the Tory faithful believed that six months ago - and almost no one did a year ago, when the party was still floundering miserably looking for a halfway credible candidate.

Last week, Downing Street let The Times know Gordon Brown thought that the game was up for Livingstone, though predictably this was later denied.

Even more problematic is the evident shortage of senior Labour figures willing to throw their weight behind the Mayor. Few London MPs or borough leaders are close to the City Hall regime; relatively few signed last month's appeal by the Left-wing Compass group.