London Mayor Boris Johnson "desperately wants to be prime minister", according to Downing Street's former spin doctor Andy Coulson.
Mr Coulson went on: "If proof were needed that our PM is a man untroubled by self doubt, it came in his next sentence - 'so I think he'll be a bloody brilliant candidate for us'.
"Stabbing David, or anyone else for that matter, in the back would be distinctly off brand - just not very Boris. He would much prefer to see David fail miserably in the election and ride in on his bike to save party and country."
More top news
Watch Hollywood heartthrob Chris Pratt doing a flawless Essex accent after revealing his wife Anna Faris is the reason behind it.
It will be breezy and wet tonight as rain sweeps in from the west, meaning a miserable start to Sunday morning.
BBC Political Editor Nick Robinson has revealed Labour tried to recruit him to be Ed Miliband's spin doctor in the run-up to the election.