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."
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