The likely departure of the White House Chief of Staff, Rahm Emanuel, to run for Mayor of Chicago is part of a half-term reshuffle of top aides that will signal a new chapter in the history of Barack Obama's increasingly embattled presidency.

It also raises a vital question: will Mr Obama continue to rely on the small and trusted group of intimates who have followed him from Chicago to Washington – or will he seize the chance to bring in new blood from the outside to invigorate an administration high command that critics say has become insular and out of touch?