Pete Rouse, 64, now one of Obama's senior advisers and his former chief of staff in the Senate, doesn't have Emanuel's larger-than-life personality or taste for colorful invective and aggressive political combat.
Instead he's a highly knowledgeable insider who's spent decades quietly advising top officials and, unlike Emanuel, rarely talks to the media.
Obama on Friday is expected to announce that Emanuel is leaving and that Rouse will replace him on an interim basis until the president decides on a new permanent chief, which could ultimately be Rouse. Emanuel is departing to run for a job he has long wanted, Chicago mayor.
Rouse has gained the respect and trust of key lawmakers during three decades on Capitol Hill, where he sometimes was referred to as the 101st Senator during years serving as chief of staff to former Senate Democratic Leader Tom Daschle.
Now, although Rouse is one of the least-visible members of Obama's senior staff, he's seen as a steady hand who can guide the White House through an unsettled period with difficult midterm elections looming and other staff changes on the horizon.
"Pete has been with senator-elect, senator, president-elect and now President Obama. There is a complete loyalty and trust with somebody like Pete," White House Press Secretary Robert Gibbs said Thursday.
"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. The type of trust that the president and others throughout this administration have in Pete is enormous."
After Obama was elected to the Senate in 2004, the same year Daschle was defeated, he recruited Rouse to help guide him through the intricacies of Capitol Hill. Rouse has said he initially resisted Obama's offer, but agreed after Obama told him he needed help building respect as a new senator - and that he had no intention of running for president in 2008.
Daschle called Rouse "the perfect person for the job" of White House chief of staff, noting that he has Obama's trust, based on years of experience, and "the best organizational mind in Washington with a network to match."
Rouse also was a key adviser on Obama's presidential transition team, and retains ties in Congress.
"During his time on Capitol Hill he developed an amazing ability to keep his name and keep himself out of the press which is why members trust him," said Jim Manley, spokesman for Senate Majority Leader Harry Reid, D-Nev., adding that Reid and Rouse have known each other for years and still talk.
"What did he bring to the table? Intimate knowledge of how the Senate works," Manley said.
Rouse, who is unmarried, was raised on the East Coast, graduated from Colby College and later got degrees from the London School of Economics and Harvard's Kennedy School of Government. He's known for his fondness for cats.
He spent time in the late 1970s and early 1980s working in Alaska as chief of staff to then-Lt. Gov. Terry Miller, a moderate Republican and friend from the Kennedy School.