After days of mulling an offer from President-elect Obama, Rep. Rahm Emanuel (D-Ill.) has accepted the job of White House chief of staff.

The news confirms a move that many of his Democratic colleagues had already been treating as a done deal, as several began eyeing bids to replace him as Democratic Caucus Chairman, the fourth-ranking slot in House Democratic leadership.

House Minority Leader John Boehner (R-Ohio) was swift to react, calling Emanuel “an ironic choice for a president-elect who has promised to change Washington, make politics more civil and govern from the center.”

Once Emanuel formally resigns his seat, by state law Gov. Rod Blagojevich (D) has five days to call a primary and special elections, which must be held within 115 days.

And there likely will be no shortage of takers for the open seat, which was once held both by Blagojevich and onetime Ways and Means Chairman Dan Rostenkowski (D).

“There are 19 Chicago alderman that represent part of that district, and I’ve heard the name of 12 of them mentioned,” said former Emanuel aide John Borovicka. “I’m surprised that I haven’t heard of any of the seven suburban mayors that represent part of the district.”

Borovicka, whose name sits atop of short list of possible Emanuel successors, said Thursday that a run is “definitely something I’m giving some thought.”

“I’ve been approached by a number of people in the district,” he said.

Borovicka, who ran Emanuel’s initial 2002 campaign, was the lawmaker’s district director until last January, when — like Emanuel before he was first elected — he became an investment banker.

Bill Daley Jr., son of Clinton Commerce Secretary Bill Daley, is also mentioned as a possible candidate in the overwhelmingly Democratic North Side Chicago district.

Matthew Murray contributed to this report.