The Sonoma County District Attorney's Office is once again a hotbed of political dissent.

Deputy prosecutor Victoria Shanahan announced Wednesday night she will challenge her boss, District Attorney Jill Ravitch, in the June election.

The move was reminiscent of Ravitch's own path to elected office that began about eight years ago. She ran unsuccessfully against then-District Attorney Stephan Passalacqua in 2006 before defeating him in 2010.

Now comes Shanahan, an ex-Mendocino County chief deputy prosecutor hired by Passalacqua in 2007, who will face similar long odds in unseating the one-term incumbent. Ravitch has won endorsements from the five-member Board of Supervisors and Sheriff Steve Freitas and is amassing funds in a campaign war chest.

But Shanahan told a gathering of supporters, including senior prosecutors, sheriff's detectives and criminal attorneys, that she felt compelled to give it a shot.

She said Ravitch has been an ineffective leader in her $205,000-a-year job, is unwilling to listen to criticism and must be replaced.

"Sonoma County deserves more than broken promises," she told a crowd of about 100 people at Cellars of Sonoma in downtown Santa Rosa. "It deserves more than failed leadership ... and compromised public safety."

Some backers who voted for Ravitch in 2010 said they, too, were concerned about the direction in which the district attorney was going. Santa Rosa defense attorney Chris Andrian, who attended Shanahan's campaign kickoff, said the fact that senior prosecutors and homicide detectives are complaining gives him pause.

"What they're telling me, I can't just blow off," Andrian said. "These are people I respect. They are the heavy lifters."

Shanahan, 44, a registered Democrat and Cloverdale resident, is married to Sonoma County Sheriff's Deputy Mike Shanahan and has two children.

She bills herself as an "anti-politician," counting on grass-roots support and endorsements from labor groups. The 250-member Sonoma County Deputy Sheriff's Association has yet to pick a candidate in the race, but its president, T.J. Van Bebber Jr., was at Wednesday's event.

He said a decision on an endorsement could come in two or three months.

"We want to get out and listen to what's being said," he said.

Shanahan didn't get into specific criticisms of Ravitch, saying she merely wanted to announce her candidacy. But she promised an "issues-based campaign" to include future public forums or debates.

Political watchers said Ravitch isn't particularly vulnerable. She's respected as a top trial lawyer and has had no major public relations disasters.

However, detractors said she's not necessarily a good manager. Some have accused her of cronyism for hiring political supporters and for excessive turnover at her Family Justice Center, which has had three leaders in less than two years. Others said she lacks transparency and is more concerned about reelection than running an office with 110 employees and a more than $20 million budget.

Most recently, her office has come under fire by crime victims who said they weren't consulted on plea bargains.

Ravitch said in a written statement she's proud of her record and looks forward to "a spirited and civil debate."

"I welcome all candidates to the race," Ravitch said in the written statement.

Shanahan was raised in Willits and graduated from Sonoma State University with a degree in environmental studies. She had a short career as a chemist at Net Pacific Inc. before attending Empire College School of Law, graduating in 2001.

She was hired by the late Mendocino County District Attorney Norm Vroman in 2002 and handled a broad range of cases before being promoted to management. Shanahan left about seven years ago after accepting a job offer from Passalacqua.

She was assigned to domestic violence, sexual assault and vehicular homicide cases, prosecuting Windsor resident Ryan Karr, who killed five family members in a fiery rear-end crash on Highway 101 in 2007. He was convicted by a jury and sentenced to four years in prison.

She was later transferred to the gang unit, where she handled the prosecution of Fernando Mendoza, charged with the 2009 slaying of rival Luis Suarez on a Santa Rosa street. Mendoza was convicted after a five-week trial and sentenced to life behind bars.

More recently, Shanahan has been assigned to review and file charges in a special court to resolve felony cases. She said her trial and management experience have prepared her to become the county's top law enforcement officer.