William Daley is resigning as President Barack Obama's chief of staff just one year into the one of the most pivotal jobs in US politics, senior administration officials say.
Mr Daley's job as day-to-day manager of the White House operation had already been changing, if not diminishing, as senior aide Pete Rouse took over more of those duties in November.
Yet Mr Daley was not expected to leave the job and return to Chicago, where his family has long held a political dynasty, until after the November presidential election.
Officials confirmed the news on condition of anonymity because the president had not yet announced it.
President Obama will now have the third chief of his staff of his presidency in the midst of a re-election year.
Mr Daley is to be replaced by Jacob Lew, now the White House budget director. The change will be effective at the end of the month.
The president chose Mr Daley to be his White House chief of staff in January 2011, but the former banker and veteran political fighter has had a somewhat rocky tenure.
At the least, the job has not seemed like the best fit.
Mr Daley had been brought in to improve relations with the business community, Republican lawmakers and others with whom he had built ties over the years. He replaced Rahm Emanuel, who is now Chicago's mayor.
He served as commerce secretary under President Bill Clinton and ran Al Gore's 2000 presidential campaign. He is the brother of recently retired Chicago Mayor Richard M Daley and the youngest son of legendary Chicago Mayor Richard J Daley.