The announcement was such a poorly kept secret that Obama joked it was "the least suspenseful announcement of all time," but it represented an important moment of transition for the presidency.
The mood at the White House reflected that this was no ordinary staff change. Cabinet members and senior staff members packed the ornate East Room, a setting often reserved for visits of heads of state, for the official word that Emanuel, the hard-charging leader of the staff, was on his way out.
Rouse, named interim chief of staff, is a calm, trusted senior adviser to Obama who has spent much of his career as a chief of staff in the Senate.
"There is a saying around the White House: `Let's let Pete fix it,' " Obama said. "And he does."
In a nod to the political sensitivities of Emanuel's move, he never directly mentioned that he was running for mayor, and Obama didn't touch that, either. Emanuel, sure to be cast as an outsider by his competitors in the upcoming mayoral campaign, did not want to announce his run from Washington.
But Emanuel did call Chicago "the greatest city in the greatest country in the world." And he told Obama, "I'm energized by the prospect of new challenges, and eager to see what I can do to make our hometown even greater." The president and Emanuel, confidants and friends, hugged three times during the event.
Rouse, befitting his style, stood quietly by the president and never spoke. Obama described him as never seeing a television camera or a microphone that he liked -- unlike the boisterous Emanuel. The differences were even apparent on stage -- Rahm stood with his trademark hands on hips; Rouse was still and stoic.
What Emanuel leaves behind is more than a staff job. It is the most demanding and influential position in the White House -- save for Obama's. The person who holds it is entrusted to shape the president's thinking, prioritize his time, manage scores of egos and issues and keep the White House focused on its goals.
The mantra in the West Wing is that no one who works for the president is irreplaceable. And yet that's how they describe Emanuel, a whirling force of ideas and energy with expertise in foreign policy, political campaigns, communications and the legislative process. Obama's aides talk of an unquestioned loss.