Boris still leads but all depends on second votes

The Evening Standard/YouGov poll found that the Tory candidate is still on course to oust his Labour rival from City Hall.

Mr Johnson leads Mr Livingstone by 44 per cent to 37 per cent on first preference votes, with Liberal Democrat Brian Paddick third on 12 per cent.

But the gap between Mr Johnson and the Mayor for the final "run-off", when second preferences are taken into account, has narrowed to its closest in the race.

The Tory MP's lead over Mr Livingstone in the "run-off " is 53 per cent to 47 per cent, a gap of six per cent. Last week, YouGov found the gap was eight per cent (54-46), a fortnight ago it was 12 per cent (56-44) and four weeks ago it was 14 points (57-43).

Liberal Democrat voters appear to be turning away from Mr Johnson, giving him his lowest level of their support since our polls began at the start of the mayoral campaign.

Only 29 per cent of Lib-Dem supporting Londoners say they are likely to give the Tory contender their first preferences, with 29 per cent also set to give them to Mr Livingstone.

Meanwhile, an increasing number of voters are worried that Mr Johnson is "not serious enough" to make an effective mayor. Those who question the Tory candidate's seriousness has risen from 34 per cent two weeks ago, to 40 per cent last week, to 43 per cent this week.

YouGov says that this appears to be the main reason why his lead in the runoff continues to narrow.

On first preferences, Mr Johnson has dropped to his lowest level of popularity during the campaign so far on 44 per cent. But he is still seven points ahead of Mr Livingstone, a slight increase on his lead of last week.

YouGov also found that Tories are much more likely to vote for Mr Johnson than Labour voters are likely to back the Mayor. Some 86 per cent of those who identify themselves as Conservatives will "vote Boris", whereas just 64 per cent of Labour supporters say they will back Mr Livingstone.

Worse still for the Mayor, some 17 per cent of Labour supporters will be voting for his rival, Mr Johnson. YouGov's figures focus on those who are most likely to vote. Among all voters, some 12 per cent say they still do not know who they will be backing and eight per cent say they will not vote.

A separate Sunday Times/MRUK Cello poll yesterday gave Mr Livingstone the lead on first preferences, with 45 per cent to 44 per cent for Mr Johnson. The poll's "run-off" figure found a dead heat on 50 per cent each.

A spokeswoman for the Mayor said the polls confirmed that the election was "now neck and neck".

"As attention concentrates on the most important policy issues and on competence to run London, Ken will pull ahead. The more Boris Johnson is seen, without his minders to shield him, the less competent he is seen to be," she said. The Johnson campaign said: "The only poll that matters is 1 May. Up until polling day, our focus will remain on communicating to voters Boris Johnson's plans to make our streets and communities safer, our transport system more efficient, our roads less congested and the need to defend our green spaces, and his determination to deliver value for money."

Mr Paddick has revealed for the first time that he has finally decided where his own second preference vote will be going - and it will be neither to Mr Johnson nor Mr Livingstone.

In a mayoral debate on the BBC's Politics Show, he said: "My job as a candidate is to get people to vote for me first preference and my responsibility as a democrat is to say to people you've got to listen to others and make your own mind up who you vote for second preference."-When pressed on who he would back, Mr Paddick replied: "My second preference isn't for either of these two and I'm not prepared to say any more than that." That leaves open the possibility he will be backing the Green Party's Sian Berry or Alan Craig of the Christian People's Alliance.

YouGov polled a weighted sample of 1,022 respondents between 16-18 April.

The latest Evening Standard Influentials debate takes place tonight at the Royal Society of Arts in John Adams Street, WC2. Tessa Jowell, Michael Gove, Tristram Hunt and Andrew Gilligan will be discussing whether Mr Livingstone deserves a third term. Some tickets will be available on the door, which opens at 6.30pm.