Rahm Emanuel Announcement Expected Friday

Updated Thursday, Sept. 30, at 12:35 p.m. ET

CBS News Chief Political Consultant Marc Ambinder says a Friday morning announcement of White House chief of staff Rahm Emanuel's resignation is all but certain. Ambinder says Peter Rouse is still the likely replacement.

Emanuel is expected to run for mayor of Chicago, Ill. He already has a campaign manager.

Ambinder reports that Emanuel would return to Chicago immediately and start collecting signatures to put his name on the ballot.

President Barack Obama has a meeting with senior advisers Thursday afternoon, a predicate for his selection of an interim chief of staff.

Emanuel was a Congressman representing Illinois' fifth district for six years before becoming Mr. Obama's chief of staff.

UPDATE: The Associated Press also reports two people close to Emanuel say he will resign as White House chief of staff on Friday to begin his mayoral campaign. Emanuel is expected to begin meeting with Chicago voters Monday and will launch a website with a message to Chicago voters.