Mayor Nutter, as he said Tuesday in his primary victory speech, wants to lead a "new Philadelphia" - and will have to do so without his chief of staff of almost four years.

Clarence D. Armbrister, Nutter's highly trusted and low-key aide, will step down shortly after the completion of budget negotiations, likely in a few weeks.

At a City Hall news conference Friday, the mayor said that Suzanne Biemiller, director of policy, planning, and coordination, would be interim chief of staff and that he would begin a search for a permanent successor.

Armbrister said he had been mulling over the decision for a while, and was discussing a position with an employer whom he declined to name.

"I'm at a point in my life where it is time to turn some pages," Armbrister, 53, said, adding that he also wanted to fulfill certain obligations to his wife and two children.

Noting that it was graduation season, he encouraged young people to enter public service, a field in which he said he would not be surprised to find himself again.

Nutter praised his No. 2 as a "peacemaker," "enforcer," "advocate," and "teacher." He said Armbrister was "out front when he needs to be, but I've never met a more selfless person who went out of the way to stay out of the limelight."

Council President Anna C. Verna lauded his "financial and administrative experience, temperament, and absolute integrity," and said, "His steady hand will certainly be missed in city government."

The smart and approachable Armbrister has overseen efforts to implement the mayor's agenda in one of the city's toughest economic climates. He is paid a base salary of $178,650.

While Armbrister is highly respected, the extent of his muscle was sometimes questioned by aides and City Council members. He was not regarded as a political operator, in a seeming reflection of what is seen as a strength and weakness of the mayor - that he is not political enough.

Armbrister's replacement will face the same challenges, including how to coordinate and oversee a staff in which authority is spread among five deputy mayors.

From the start, Nutter sought to give Armbrister the maximum say-so, frequently stating that talking to his chief of staff was the same as talking to him.

"Some things a mayor can't do - or shouldn't be involved in doing - often fall on the plate of the chief of staff," the mayor said as understanding colleagues chuckled. He said Armbrister, a friend for 25 years, "set a new standard for chief of staff in the city of Philadelphia."

Preparing Biemiller for the job, Armbrister recounted a note he received from his predecessor, Joyce Wilkerson - along with a club. The note said: "I hope you never have to use it, but feel free to if you need to."

A Miami native and a lawyer, Armbrister was city treasurer under Mayor Ed Rendell in 1994. He went on to become managing director of the School District of Philadelphia for four years before joining UBS Paine Webber in 1998 as director of the municipal bonds division.

From 2003 to 2008, he was Temple University's chief operating officer.

Armbrister and Nutter both graduated in 1979 from the University of Pennsylvania. His wife, Denise McGregor Armbrister, is one of five members of the School Reform Commission.

While saying little about his next professional move, Armbrister's departure means he is free to pursue his dream job: general manager of the Miami Dolphins.

Contact staff writer Marcia Gelbart at 215-854-2338 or mgelbart@phillynews.com.