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Some in Downing Street say it is now accepted that – unless Cameron falls victim to events – Boris will not get a chance to challenge for the leadership until after the Prime Minister wants to move on. At least initially, Downing Street sources refused to give a ‘moment’s thought’ to Boris not serving a second term as Mayor: ‘We just believe he will win.’ In the Tory high command, thoughts were already turning to a potential Boris v. George Osborne contest after 2016, when it is believed likely that Cameron will step down to ‘pursue other interests’. But as the architect of the Cameron government’s divisive austerity plan, Osborne may find himself ruled out and in any case, chancellors rarely go on to make a success of the top slot. Moreover,
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Sonia Purnell (Just Boris: A Tale of Blond Ambition: A Biography of Boris Johnson)