(CNN) -- Rahm Emanuel, President Obama's chief of staff, is known as a force of nature who efficiently navigates the back halls of Congress to get exactly what he wants.
Now it appears he wants to navigate city hall in his hometown of Chicago, Illinois. Three Democratic sources close to Emanuel say he's all but certain to run to replace retiring Chicago Mayor Richard Daley and leave the White House.
An announcement is expected to be scheduled for Friday, sources said.
Emanuel is an aggressive political animal who has been known to punctuate his arguments with the F-bomb. Most agree it's not because he's an angry man -- it's just part of his foul-mouthed repertoire.
His colorful reputation is regularly the subject of Obama's quips. Obama joked at the White House Correspondents Dinner this year that Mother's Day was a difficult holiday for Emanuel because "he's not used to saying the word 'day' after 'mother.' "
But there's so much more to Rahm than his mouth.
In fact, he's missing half a finger from a freak accident as a young man, toiling away in the hardscrabble fast food industry.
Some opponents who have butted heads with Emanuel have reported feeling uncomfortable as he wagged his nub in their faces during heated negotiations.
His bigger-than-life personality, stuffed into a small frame, was honed in the notoriously cutthroat world of politics in his native Illinois.
He was a senior adviser and top fundraiser for Daley, and he played a similar role in President Bill Clinton's early presidential bid and then later in the Clinton White House.
He also ran his own successful campaign, becoming U.S. representative from Illinois' 5th District in 2002. It was a seat previously occupied by Rod Blagojevich, who has gone on to become the state's latest controversial political figure.
And while he's considered a member of Obama's so-called "Chicago Mafia," unlike close friend David Axelrod, Emanuel was not in Obama's inner circle from the start. In fact, Emanuel indicated he would support then-Sen. Hillary Clinton long before she even threw her hat into the presidential race.
So when the real race got under way, Emanuel found himself in a political jam. Should he go with Clinton, the candidate he once said he would back? Or, would hometown loyalty be too powerful to resist? Obama's eventual chief of staff, faced with an impossible choice, opted to stay neutral until after the final primary.
Love him or hate him, everyone seems to agree that his role in shaping the president's agenda, from health care to economic proposals, cannot be understated. Emanuel makes frequent trips to Capitol Hill, where Democratic and Republican sources say he uses a mix of harsh reality and institutional knowledge to try to coax skeptics onboard.
That is precisely why Obama hired the adviser some call "Rahmbo."
But even Hollywood's "Rambo" is finally forced to surrender after a hostile battle. So is Emanuel, tired and bruised after nearly two years of intense political fights, really ready to call it quits in D.C., to make a run for mayor of the Windy City?
A well-connected Chicago political observer says the time is right for Emanuel to pounce. "He knows the city and loves the city and the window is open," said the source.
CNN Chief National Correspondent John King contributed to this report