Mayor Kenney lost his chief administrative officer Wednesday when City Controller Alan Butkovitz gained a Democratic primary election challenger.
Rebecca Rhynhart resigned her position on Kenney's staff, saying she would be a candidate in the May 16 election for controller.
Rhynhart, who served in all eight years of Mayor Michael A. Nutter's administration, first as city treasurer and then as budget director, said: "We deserve more from our city controller."
Butkovitz, a former state representative, is seeking a fourth term.
"He's been in office for over a decade," Rhynhart said. "He's been in elected office for close to 25 years. I think some new blood is a good thing."
Butkovitz on Wednesday dismissed Rhynhart as a "put-up candidate" by Nutter. Butkovitz and Nutter clashed in August over Butkovitz's audit of the Mayor's Fund for Philadelphia.
Butkovitz said Nutter and his staff used more than $380,000 from the fund as a "slush fund."
Nutter responded by calling Butkovitz "a liar, a snake, and a hypocrite."
Butkovitz, 64, said Rhynhart was "moving in the wrong direction" and should have stayed in the job Kenney created for her when he took office in January.
"She's been at the center of budgetary decisions and disasters for the past eight years," he said. "For her to argue now that she's an outsider with some good ideas, the question is, why didn't she use them then?"
Kenney said in a statement released by his staff that Rhynhart "has done a great job during her tenure as CAO, spearheading procurement reform and modernizing city purchasing practices. I wish her well."
Through a spokesman, Kenney declined to comment on Rhynhart's entering the controller's race.
Butkovitz said he called Kenney Sunday evening after the Inquirer first reported on Rhynhart's impending candidacy.
He said Kenney told him that "it was news to him."
Kenney had already agreed to be cochairman of his campaign and to help raise money, Butkovitz added.
Butkovitz's claim apparently came as news to Kenney. Marty O'Rourke, a spokesman for Kenney's political action committee, said the mayor would not cochai Butkovitz's reelection campaign.
"He doesn't think he should be cochair of either campaign because the controller is the office that audits the city," O'Rourke said.
Nutter did not respond to a request for comment.
Rhynhart, 42, has a master's degree in public administration and worked in finance for seven years before joining Nutter's administration in 2008.
She said she never imagined seeking public office.
"Nine years ago, I left a job in the private sector and took a large pay cut to come work for the City of Philadelphia and make it better," Rhynhart said.