As he prepares to take office, President-elect Barack Obama is relying on a small team of advisers who will lead his transition operation and help choose the members of a new Obama administration. Following is part of a series of profiles of potential members of the administration.

Name: Rahm Emanuel

Chosen for: Has accepted Mr. Obama's offer to be the White House chief of staff.

Will bring to the job: An unusual hybrid of high-level experience as a top adviser to President Bill Clinton together with proven expertise as a Congressional leader and political strategist. Mr. Emanuel is also a close friend of Mr. Obama, a fellow Chicagoan.

As the No. 4 Democrat in the House and an architect of the Democratic majority, Mr. Emanuel knows Congress from the inside out after winning his seat in 2002. In the Clinton administration, he was aggressive, frequently profane and instrumental in shaping domestic policy on issues like health care, welfare and trade.

He earned the nickname Rahmbo for his determination and take-no-prisoners approach — an advantage when trying to bring a thorny issue to resolution, but a style that can be off-putting to those accustomed to gentility. In resigning his seat, Mr. Emanuel will be relinquishing a promising House career and aspirations to become speaker.