Who has left the White House so far?

Chief of Staff Rahm Emanuel has now joined a handful of top White House aides who have headed for the door, less than two years into President Barack Obama's term. Mr Emanuel's departure could signal a profound shake-up for a White House built around strong personalities.

But it is not unusual for White House staff to turn over at this point in an administration. Here are other top staff who have left.

Rahm Emanuel, Chief of Staff

Mr Emanuel left the White House amid growing speculation he planned to run for mayor of his native Chicago. Two years is a typical tenure for White House chief of staff, a job that brings gruelling hours and unforgiving pressure, and Mr Emanuel's departure was widely anticipated.

Famously hard-hitting and foul-mouthed, Mr Emanuel, 50, is a former Chicago congressman, White House aide and investment banker, whom Mr Obama selected for his connections in the Democratic congress, his White House experience and, perhaps, for his aggressive manner.

Among the accomplishments Mr Emanuel can claim as he heads home are the president's healthcare overhaul and financial regulatory reform.

But he leaves ahead of what is expected to be a bloodbath for the Democrats in the November mid-term elections. And on Mr Emanuel's watch the Republicans have bested the president on several key policy areas, including the lifting of the ban on openly-gay military personnel and legislation to limit carbon emissions.

General James Jones, National Security Adviser

The departure of Gen James Jones from the post of national security adviser, announced on 8 October, had long been trailed in the media.

It was suggested by pundits that the retired general did not have a good relationship with President Obama or his inner circle of advisers and senior officials.

The general acted as the president's chief adviser on national security, with an office inside the White House.

Gen Jones was appointed to the post in 2008, having retired the previous year from the Marine Corps after 40 years of service.

His tenure has been much shorter than the previous five holders of the post, who averaged about four years in the role.

The general is being succeeded by Tom Donilon, his deputy.

Ellen Moran, Communications Director

Ms Moran lasted less than three months in the Obama administration, announcing her sudden departure in April 2009.

Previously director of Emily's List, an organisation dedicated to supporting liberal women in politics, Ms Moran was one of just a handful of senior staff who had not worked on the Obama campaign.

She was also one of only a few women in senior positions in the Obama White House.

Some commentators speculated that Ms Moran had had a difficult time breaking into Mr Obama's tight-knit circle of close advisers - most of whom had worked with the president for many years - making it hard for her to carry out her role.

She left to become chief of staff to Commerce Secretary Gary Locke.

Van Jones, Special Adviser for Green Jobs

Mr Jones, a long time environmental activist, became the target of conservative outrage over his previous political activities and resigned amid controversy in September 2009.

Enraged conservatives, led by Fox News host Glenn Beck, charged that his former involvement with a San Francisco area radical group and his signing of a petition asking whether Bush administration officials "may indeed have deliberately allowed 9/11 to happen, perhaps as a pretext for war" made him an unsuitable public official.

He was accused of being a Marxist, and was caught on videotape using a swearword to describe conservatives.

As the campaign to oust him gathered steam, Mr Jones resigned, saying that he had been the victim of a "vicious smear campaign", but he could not "in good conscience ask my colleagues to expend precious time and energy defending or explaining my past".

Mark Lippert, Deputy National Security Adviser

Mr Lippert had worked for Mr Obama since 2005, when he was appointed as the then-senator's foreign policy adviser.

The two men were both colleagues and friends - they used to play basketball together - and Mr Lippert was considered part of Mr Obama's "inner circle" of advisers during his presidential campaign.

His resignation in October 2009 came as a surprise. Many thought he was being groomed for an even more senior role.

Instead he chose to rejoin the US Navy, after being a reservist for several years.

Greg Craig, White House Counsel

Mr Craig announced his decision to resign in November 2009, while President Obama was travelling in Asia.

Mr Craig, who had worked for President Bill Clinton, Senator Ted Kennedy and Secretary of State Madeleine Albright, was both a friend and adviser to Mr Obama during the 2008 presidential campaign.

But his role in overseeing the closure of the detention facility at Guantanamo Bay was a poisoned chalice.

Significant political pressure rendered him unable to deliver on the promise, and he was blamed for the Obama administration's perceived missteps in handling the matter.

Some reports indicated Mr Craig was forced out of the administration by disgruntled advisers who believed that both he and the Guantanamo issue had become a serious liabilities.

Others portrayed him as the fall guy for the failed policy as well as controversies over torture.

Peter Orszag, Office of Management and Budget Director

The Office of Management and Budget (OMB) manages the federal budget - overseeing spending, analysing the effectiveness of federal agencies and advising the president on budgetary decisions. Mr Orszag held this critical post during the worst of the economic crisis, but decided to call it quits in June 2010.

Mr Orszag was a prominent public figure. His position made him a key advocate for the economic stimulus.

But he also generated headlines of his own - fathering a child with his ex-girlfriend just weeks before becoming engaged to an ABC News correspondent who he had dated for seven months.

Since leaving the White House he has become a contributing columnist for the New York Times. His first piece reportedly raised the hackles of some his former colleagues, who viewed it as critical of President Obama.

Christina Romer, Council of Economic Advisers Chair

Ms Romer played a pivotal role in crafting and overseeing the stimulus package. Cheerful and articulate, Ms Romer became one of the administration's most useful economic advocates on television news programs.

Ms Romer had signalled early in her tenure that her work in DC would be temporary.

She chose to return to her previous post as an economics professor at the prestigious University of California, Berkeley, in September.

The White House cited family commitments as the reason for her departure - her teenage son started high school this semester.

But her timing coincided with one of the most sought after positions in America's federal banking system - president of the Federal Reserve Bank of San Francisco - became available. She is probably being considered for the position.

Larry Summers, National Economic Council Director

Mr Summers recently announced that he had resigned his post and will return to his previous job as a professor at Harvard following November's midterm elections.

Mr Summers, an acclaimed economist and experienced presidential adviser, has attracted controversy throughout his career.

He was ousted as president of Harvard by his academic peers after he commented that the dearth of women working in science may be the result of a biological gender disparity.

In the White House, he quickly gained a reputation from some for brusqueness and arrogance. He reportedly had tense relationships with other members of Mr Obama's economic team, and his ties to Wall Street aggravated some in the Democratic left.