White House chief of staff Rahm Emanuel hasn't yet decided whether he'll leave the administration and run for mayor of Chicago. But with aides saying that they'd be surprised if he didn't, speculation has begun over who his potential replacement might be and what staffing shake-ups might follow.
The departure of Emanuel, the man considered the administration's chief operating officer, would come at a crucial time for the White House, which faces sagging poll numbers and the prospect of losing Democratic majorities in Congress in November.
The move could be a chance for the White House to retool its operations, but some observers expect the president would replace Emanuel with someone close to the inner circle and with experience inside an administration.
Vice President Biden's chief of staff Ron Klain, White House senior advisor Valerie Jarrett, Deputy National Security Advisor Tom Donilon and White House deputy chief of staff Jim Messina are all said to be on the list of candidates, should a replacement need to be named.
Yet the choice may also be made to appoint someone from outside the administration -- someone who could bring fresh perspective and energy at a time when the White House may need it the most.
The former Senator Majority Leader, Tom Daschle, and Obama's 2008 campaign manager, David Plouffe, are both said to be on the list of names to be considered from outside the administration.
Emanuel's departure is not widely expected to trigger a mass exodus, however, with two years to go before the end of Obama's first term.
"I think there's no doubt that there will be people that return to their lives and their families," White House press secretary Robert Gibbs said of the typical turnover that occurs within presidential administrations. "But we've got a while before that. We've got at least two months before this election -- or about two months before this election before we get to a lot of those decisions."
Senior White House advisor and fellow Chicagoan David Axelrodsaid he is not thinking about turning in his White House pass anytime soon.
"I am certainly going to be here for a while and we have a lot of work to do," Axelrod told ABC's Ann Compton. "I am very committed to this President and I think he's got the best interests of the American people at heart and he's working his heart out and I want to support him in that. At some point, I'm going to leave. I've been very candid about that. We have a reelection campaign to think about and I'll turn my attention to that, but that's off in the future."
Emanuel has not been coy about his personal goal to be the mayor of his hometown, telling PBS' Charlie Rose in April, "One day I would like to run for mayor of the city of Chicago.... That's always been an aspiration of mine even when I was in the House of Representatives."
Longtime Chicago mayor Richard M. Daley's announcement Tuesday that he would not seek reelection in February seemed to create the opportunity Emanuel has been looking for.
And Axelrod today said President Obama would give his blessing should Emanuel decide to go.
"The mayoralty in Chicago is an unbelievably attractive opportunity," he said. "And I'm sure if Rahm decides to do that, the president will support that decision."
Emanuel would have to declare his intent to enter the race by Nov. 22. The election would be in February 2011.
Emanuel would join a number of top administration officials who have already moved on this year, including members of the president's economic team, former Office of Management and Budget director Peter Orzsag and advisor Christina Romer.
While the Obama administration has not yet faced a major shake-up, the first term has been marked by several contentious resignations and public battles over some nominees who never even got the job.
In September 2009, Van Jones, President Obama's Special Advisor for Green Jobs at the Council on Environmental Quality resigned amid controversy over remarks he made alleging "evidence that suggests high-level government officials may have deliberately allowed the September 11th attacks to occur."
Two months later, White House general counsel Greg Craig also resigned after weathering criticism from within the administration over his role in the crafting the administration's policy on the Guantanamo Bay detention center closure and the release of detainee interrogation records from the previous administration.
But perhaps the most high-profile departure to date from the Obama administration happened before the individual could even be confirmed. Former Senator Daschle withdrew his nomination to be secretary of health and human services after complex tax problems were uncovered.
So far, departed veterans of the Obama White House have not followed in the footsteps of Paul O'Neill, who famously left early in George W. Bush's first term and publicly aired his differences with the administration. But many of those from the inside typically get book deals.
ABC News' Ann Compton contributed to this report.