Oct. 1, 2010 -- President Obama, as expected, announced today that his chief of staff, Rahm Emanuel, will leave Washington to explore a run for mayor of Chicago. The president named senior advisor Pete Rouse as his interim chief of staff.
"This is a bittersweet moment," the president said, as he praised Emanuel, adding that "we could not have accomplished what we accomplished without Rahm's leadership."
The president also praised Rouse as a can-do person. "There's a saying around the White House, 'Let's let Pete fix it' and he does," the president said.
Rouse brings a wealth of experience to the job, including over 30 years serving as a chief of staff to various members of Congress including former Senate Majority Leader Tom Daschle, D-S.D. Rouse's influence and experience earned him the nickname The 101st Senator.
Rouse also brings a low-key temperament, in contrast to Emanuel's hard-charging style. Administration officials say Rouse's demeanor will suit the White House well at this point in time.
White House Press Secretary Robert Gibbs has emphasized the long history and relationship between Obama and Rouse.
"Pete has been with [Obama as] Senator-elect, Senator, President-elect, and now President Obama," said Gibbs. "There is a complete loyalty and trust with somebody like Pete. Pete's strategic sense has played a big part in the direction of virtually every big decision that's made inside of this White House."
Gibbs said that the type of trust that Obama and the administration staff have for Rouse is enormous.
Also enormous? The job Rouse is about to step into.
When former West Wing staffers were asked to describe the role of the White House chief of staff, words like coordinator, enforcer, confidant, counselor, and leader were frequently used.
The job is all-consuming; the hours are never-ending, the demands and pressures immense.
"You are the principle person, the architect, with the president day in and day out," said former Reagan chief of staff Ken Duberstein.
Chief of Staff: White House Point Man
University of Akron political science professor David Cohen is writing a book on the subject: "Catching the Javelin: The Chief of Staff in the Modern White House."
According to Cohen, the chief of staff can have a fingerprint on nearly everything that comes up at the White House – making the trains run on time, managing personnel, guiding policy and politics and representing the administration's perspective in interviews.
"I don't think there is a more critical position. You can look at the modern presidency and correlate a successful president with a successful chief of staff," Cohen said. "A good chief of staff can really help a president achieve his goals.
"When things are going really well, it's a great job. But when it's not, well it's tough," Cohen said.
Dan Bartlett , counselor to former President George W. Bush, said that turning to someone like Rouse was a smart move in order to facilitate a smooth transition, rather than turn to someone with "their own political profile and ego that could bump up against the president."
The average tenure for a chief of staff in the modern White House is about two-and-a-half years. George W. Bush's first chief of staff Andy Card broke that mold, serving nearly five-and-a-half years.
Several people with West Wing experience said that one critical trait a chief of staff needs to bring to their work is the ability to provide the president with solid counsel.
"At the end of the day it's the chief of staff's responsibility to create a comfort zone around the president, a comfort zone where the president can make good decisions and make sure things are getting executed properly," Bartlett said.
White House Chief of Staff: Conductor, Counselor and Confidant
Several former West Wing aides said that the White House staff looked to the chief of staff for clues about the president's mood.
Former spokeswoman Dana Perino served in the West Wing during George W. Bush's second term and said that the chief of staff needs to be an anchor for the president's staff.
"A chief helps keep things in perspective, can help you deliver bad news to the boss -- that you feel has your back when you're not in the room," Perino said. "It also is someone that keeps everyone on their toes to avoid mistakes."
Bartlett said one crucial role for the chief of staff that perhaps goes unnoticed outside of the West Wing is managing the president's Cabinet.
"Well you can imagine the collective egos of the people serving in the Cabinet. None of them are ever happy about the role they're playing in policy making, their access to the president," Bartlett said. "The chief of staff decides what type of access the Cabinet gets, where they contribute, how they contribute."
Working Capitol Hill
An equally important part of the job description is the work done at the other end Pennsylvania Avenue – Capitol Hill.
Emanuel came to the White House after serving six years in Congress. Administration officials said that experience was crucial during the push to develop and pass the health care reform bill.
"The White House has its legislative staff but ultimately it can be the chief of staff that cuts the deal with Congress," said Bartlett.
Never a Good Time for Staff Shake-Ups
With the clock always ticking and President Obama's to-do list not getting any shorter, there is perhaps never a good time for significant staff turnover, former White House officials said.
Emanuel's Influence Widely Felt
The loss of Emanuel will be felt throughout the Obama White House, especially in the final weeks before the crucial mid-term elections.
"The person who did the strategy and the tactics, the person who coordinated for the administration, working with the leadership in the house and the senate was Rahm," said former Reagan chief of staff Ken Duberstein. "So whether you agree or not that the legislation was helpful, it was part of the president's agenda and on the legislative agenda, Rahm was the driving force."
White House spokesman Gibbs said Emanuel's influence has been felt on every key decision and accomplishment over the last two years.
Emanuel may not be as visible as Gibbs but he still maintained a public presence with Sunday morning talk show interviews and sit-downs with network anchors. Based on his personality and looking at his low-key past, it is unlikely that Rouse will step in and become a fixture on the airwaves.
In fact at the White House event today where the personnel moves were announced, the different styles of the outgoing and incoming chiefs of staff was apparent.
Emanuel is expected to make remarks. Rouse will not.
ABC News' Jake Tapper, Arlette Saenz and Sunlen Miller contributed to this report.