The Tory Mayor enjoyed the support of 40 per cent of those who expressed a view. David Cameron had the support of 33 per cent of those surveyed.
Likely Tory contender in a future leadership contest Theresa May trailed both Johnson and Cameron on just 18 per cent, according to YouGov poll conducted for the Evening Standard. At the bottom of the race were chancellor George Osborne with six per cent and foreign secretary Philip Hammond on three per cent.
Among Conservatives, the Mayor polled 35 per cent, well ahead of rivals in the cabinet, none of whom managed to break into double figures. Ukip Londoners opted for the Mayor by 44 per cent to David Cameron's 26 per cent.
While Johnson won out in the in opinions of the wider London public, Tory supporters, for the moment, appear willing to give David Cameron the benefit of the doubt. More than half of Conservative supporters in London support David Cameron's leadership.
Cameron could find his support among Conservatives rapidly diminish if he fails to beat Ed Miliband. If the Tories fail to secure a majority in May, it will be over two decades since the party won a General Election outright.
David Cameron will have a hard time explaining to his party why he couldn't achieve victory against the most unpopular leader in Labour's history. Speaking to the Evening Standard, YouGov's Tanya Abraham said:
While a majority of Tory voters with an opinion on the issue say at present that they would want David Cameron to stay in charge of the party if there were a second General Election this year, Boris scores well outside the party faithful. The Mayor sweeps up among both Labour and Ukip voters where he has a large lead.