Voters much prefer Boris Johnson to David Cameron, according to an opinion poll.
The survey Opinium for The Observer gave the London mayor a net +30% compared to -21% for the Prime Minister.
The wide gulf between the two old rivals is likely to intensify speculation about Mr Johnson's long-term leadership ambitions as Conservatives gather for their annual conference in Birmingham.
The poll also showed a strong pick-up in Ed Miliband's approval rating, which has risen to -10% following last week's Labour Party conference - his best showing in an Opinium poll.
Deputy Prime Minister Nick Clegg, however, continues to languish on -48%.
Overall Labour enjoyed only a small post-conference bounce, up two points on 41%, an 11 point lead over the Tories, who are up one point on 30%, with the Liberal Democrats on 9%.
Opinium surveyed 1,965 UK adults aged 18 and over online between October 2 and 4.