University of California President Janet Napolitano, who oversaw historic expansions of the 10-campus system and championed immigrant students, but whose management structure faced criticism and embarrassing scrutiny, said Wednesday she will step down in August 2020.

Napolitano, a former homeland security secretary and Democratic governor of Arizona, made the announcement at a meeting of the university system's Board of Regents in Los Angeles.

FILE: University of California President Janet Napolitano attends a meeting of the UC Board of Regents in San Francisco.

FILE: University of California President Janet Napolitano attends a meeting of the UC Board of Regents in San Francisco. (AP)

"My time at UC has been deeply gratifying and rewarding. I have been honored and inspired every day to serve this institution alongside incredibly dedicated, passionate people," Napolitano said in a statement. "The decision was tough — and this moment, bittersweet — but the time is right."

Napolitano, 61, has battled a recurrence of breast cancer but said her health is good and did not play a role in her decision to step down.

"All of my tests are clear. So that was not a factor in my decision," Napolitano told reporters in a conference call, saying she will complete her seventh year in the job before stepping down.

"It seemed like a good time to have some fresh blood at the University of California," she said.

During her tenure, Napolitano has overseen an expansion of the public university system, enrolling historic numbers of students and making it easier for in-state students to transfer from community colleges to the university system.

She oversaw reforms of policies on sexual misconduct and was a stanch supporter of the rights of immigrant students.

FILE: University of California President Janet Napolitano at a meeting of The Commonwealth Club in San Francisco. 

FILE: University of California President Janet Napolitano at a meeting of The Commonwealth Club in San Francisco.  (AP)

In 2017, the university joined a lawsuit challenging the Trump administration's decision to rescind the Deferred Action for Childhood Arrivals program, an action that led to injunctions that allowed hundreds of thousands of DACA recipients to extend their authorization to legally live and work in the U.S., including students in the UC system.

But Napolitano also was criticized by state lawmakers after a state audit found problems with her office's financial management. A report from State Auditor Elaine Howle in 2016 found that Napolitano's office failed to disclose millions of dollars in reserve funds.

It also said Napolitano's top aides had sought to suppress campus criticism of her office in surveys that were supposed to be confidential and sent directly to the state auditor.

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The investigators found that Napolitano had approved of the plan to review the survey responses. The audit said there was "insufficient evidence" to conclude that she knew of the full range of what her staff was up to or that she directly approved of any interference. But the investigation and subsequent oversight prompted a rare public rebuke by the UC's governing Board of Regents.

Napolitano had a distinguished career before coming to California. As a partner in a prominent Phoenix law firm, she represented Anita Hill during the Senate Judiciary Committee's confirmation hearings for Supreme Court Justice Clarence Thomas in 1991. Hill accused Thomas of sexual harassment, which he denied.

She was a popular Democratic leader in Republican-controlled Arizona, easily winning re-election by more than 25 points in 2006. She stepped down in 2009 to join President Barack Obama's cabinet as secretary of homeland security, overseeing border security, ramped-up immigration enforcement and efforts to prevent terrorism. She served until 2013, when she became UC president.

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Napolitano said she will take a year sabbatical before teaching, beginning in the fall of 2021, at the University of California, Berkeley's Goldman School of Public Policy, where she is currently a tenured professor.

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Napolitano was asked by reporters if she would rule out running for public office or accepting a political post or appointment.

"I have no intention in those regards, but you never say never," she said.