Boris Johnson would give the Conservative party a six-point bounce, if he replaced David Cameron as leader, according to a new poll.
Research by YouGov for The Sun put the party's current level of support at 31% - well behind Labour on 42%.
But that advantage would be virtually wiped out if the London mayor took charge.
Some 37% said they would back the Conservatives under Mr Johnson while Labour dropped to 38%.
The Mayor's popularity has surged following the success of the London Olympics and he's criticised the Prime Minister over a potential U-turn on Heathrow airport expansion. But he has flatly denied claims that he is manoeuvring himself into a position to take the Tory leadership.