Rahm Emanuel, Barack Obama’s chief of staff, has announced his resignation to run for mayor of Chicago, the US president confirmed today.
"We are all very excited for Rahm as he takes on a new challenge for which he is extraordinarily well qualified," Mr Obama said in the East Room of the White House.
"It is fair to say we could not have accomplished what we accomplished without Rahm's leadership," he added.
Peter Rouse, a senior adviser to Mr Obama and his former chief of staff in the Senate, will take over on a temporary basis.
Mr Emanuel engineered the Democrats’ 2006 legislative victory and has played a key role in the Obama administration.
The move comes only a week after Mr Obama’s top economic adviser, Larry Summers, announced he was returning to his professorship at Harvard. Peter Orszag resigned as budget director in July, and Christina Romer, who chaired Mr Obama’s economic council, left the White House in August.
David Axelrod, Mr Obama’s closest and most trusted aide, is expected to leave in the spring, to prepare the president’s campaign for re-election.