WASHINGTON, Sept 30 The exit of top aide Rahm Emanuel and other staff changes give President Barack Obama a chance to signal a fresh start as he tries to boost his weak poll numbers and prepare for his 2012 re-election campaign.
White House officials said Emanuel's departure and that of other senior aides, such as top economic adviser Larry Summers, would mean a loss of valued players.
But outside analysts said that with Obama's approval ratings mired near 45 percent, he could use the changes to signal he is hitting the "reset" button on his presidency at a time when his Democrats fear big losses in the Nov. 2 congressional elections.
Here is a list of the changes that have taken place and are in store for the Obama administration.
WHITE HOUSE CHIEF OF STAFF RAHM EMANUEL
Obama's hard-charging senior aide plans to leave the administration to run for mayor of Chicago. Emanuel holds broad sway over policy and legislative strategy and even over who meets with the president. Sources said he would formally announce his plans on Friday.
Potential successors include:
* Senior adviser Pete Rouse. The longtime Obama aide is expected to fill in for Emanuel on an interim basis but may not end up as the permanent replacement.
* Deputy national security adviser Tom Donilon. Donilon, who has served in senior roles in the State Department and is close to Vice President Joe Biden, has a milder temperament than Emanuel. But Donilon is known as one of the White House's hardest working staffers and associates describe him as highly effective. He has developed a strong rapport with Obama.
* Ron Klain, chief of staff to Biden. Klain also served as a top aide to former Vice President Al Gore. He is said to enjoy his current job and may not want to make a change.
* White House counsel Robert Bauer. Bauer has been a longtime adviser to Obama and served as his personal attorney.
* Former Senate Democratic leader Tom Daschle. Daschle, a senior Democrats whose counsel Obama values highly, had been nominated by the president early in his term to become Health Secretary but a flap over unpaid taxes led him to withdraw.
* Leon Panetta, currently the CIA director, was chief of staff to former President Bill Clinton.
LARRY SUMMERS, DIRECTOR OF THE WHITE HOUSE NATIONAL ECONOMIC COUNCIL
Summers has said he will leave the administration by the end of the year to return to Harvard University, where he is a professor. Obama is being urged by some to tap someone with a business background for Summers' job, saying it would help heal a rift between the White House and the business community.
But many White House aides -- including Summers -- say Obama will focus on finding the best person for the job.
Possible replacements for Summers include:
* Anne Mulcahy, a former Xerox Corp. chief executive, has been considered a leading candidate. But she said on CNBC on Thursday that she did not feel the job was a good fit for her, and that other candidates might be better.
* Laura Tyson, a former top economic adviser to former President Bill Clinton, is a professor at the University of California, Berkeley.
* Diana Farrell is a deputy to Summers at the National Economic Council. As a former analyst at Goldman Sachs and former director at the McKinsey Global Institute, she would bring business expertise.
* Jason Furman, also a deputy to Summers, was a top economic adviser to Obama during his presidential campaign.
SENIOR WHITE HOUSE ADVISER DAVID AXELROD
Axelrod has indicated he will likely leave the administration sometime in 2011 to help lay the groundwork for Obama's 2012 re-election campaign.
Many speculate that White House press secretary Robert Gibbs would then move into a more behind-the-scenes role advising Obama on strategy and communications. Gibbs' deputy, Bill Burton, is seen as a top contender to fill Gibbs' job behind the podium.
GENERAL JAMES JONES, NATIONAL SECURITY ADVISER
Democratic sources say Jones is likely to leave his post by the end of this year. He is the point person for coordinating foreign policy advice to the president. Replacements could be:
* Donilon, who is also a leading candidate for White House chief of staff, could be considered for a promotion to Jones' job.
* General James Cartwright, vice chairman of the Joint Chiefs of Staff, is referred to by Obama as his "favorite general," according to a new book by journalist Bob Woodward.
* White House counter-terrorism adviser John Brennan.
* Deputy Secretary of State James Steinberg. Steinberg was deputy national security adviser in the Clinton administration and advised Obama during his 2008 campaign.
DEFENSE SECRETARY ROBERT GATES
Gates, a holdover from the Bush administration, has signaled his intention to resign sometime in 2011.
Contenders to replace him include:
* Michele Flournoy, undersecretary of Defense for policy, who would become the first female Defense chief.
* Democratic Senator Jack Reed, an Army veteran. Reed is someone whose counsel Obama values, Democrats say.
* Chuck Hagel, a former Republican senator and a Vietnam War veteran.
ADMIRAL MIKE MULLEN, CHAIRMAN OF THE JOINT CHIEFS OF STAFF
Mullen, the top U.S. military officer, is expected to retire once he completes his second term on Oct. 1 next year.
* General David Petraeus, currently commanding the war in Afghanistan, would seem to be a natural fit for the job but it is unclear whether Obama would want to pull him from the field after just over a year.
* General James Cartwright, vice chairman of the Joint Chiefs of Staff, is considered a strong contender for Mullen's job.
TOP ADVISERS WHO ALREADY HAVE LEFT THE ADMINISTRATION
* Christina Romer departed as chairwoman of the Council of Economic Advisers at the beginning of September. She was replaced by Austan Goolsbee, who had been a member of the CEA.
* Peter Orszag, manager of the White House Office of Management and Budget, left in July. Obama has nominated Jacob Lew, deputy Secretary of State for management and resources and chief operating officer of the State Department, to replace him; Lew has not yet been confirmed by the Senate. (Additional reporting by Phil Stewart and Patricia Zengerle; Editing by Xavier Briand)