Los Angeles County Sheriff Lee Baca's surprise retirement announcement Tuesday upended the election campaign to lead the nation's largest sheriff's department and added new complexities to reform efforts after a series of scandals and an ongoing federal criminal probe. With Baca out of the race, the field of candidates is expected to widen in what will be the first sheriff's election without an incumbent in more than 50 years.

Immediately after Baca's announcement, one of his assistant sheriffs, Todd Rogers, declared his candidacy.

"My calling card will be 'Back to basics,'" said Rogers, a councilman in Lakewood, who added that Baca had been poorly served by previous top managers. "There has been catastrophic failure of leadership in the Sheriff's Department."

Another assistant sheriff, James Hellmold, said he was also considering a run but has not made a decision.

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"I am a crime fighter," he said. "I am not a politician."

Baca described both men as highly qualified to succeed him but stopped short of offering a formal endorsement.

Former Undersheriff Paul Tanaka and former Cmdr. Bob Olmsted had been considered the main challengers in the race. Retired Sheriff's Lt. Patrick Gomez and Los Angeles Police Det. Lou Vince are also running.

"You'll see a number of candidates come out now because the sheriff's not running," said Supervisor Don Knabe. "It changes the dynamics."

Sheriff hopefuls would have to move quickly. The deadline to enter the race is in March, and serious contenders will need to raise enough money to reach voters in a county of 10 million residents before the June primary.

One key question is whether the race will generate a strong candidate from outside the Sheriff's Department who cannot be tied to any of the agency's various problems.

Long Beach Police Chief Jim McDonnell would fit that mold. McDonnell, who served as second in command to L.A. Police Chief William J. Bratton before moving to Long Beach, was one of seven members of a county commission that investigated allegations of excessive force against county inmates and faulted Baca's management of the jails. He weighed a run last year but decided against challenging Baca, citing the difficulty in raising money to unseat an incumbent.

"I have been strongly encouraged to enter the race, and I am willing to give it a fresh look," McDonnell said Tuesday.

LAPD Deputy Chief Terry Hara, 56, said he too is weighing a bid.

Baca's exit also raises concerns about the fate of department reforms. He had expressed a commitment to cooperate with a new inspector general appointed by the Board of Supervisors to oversee his agency and this week endorsed a plan to set up a permanent civilian oversight commission.

Supervisor Zev Yaroslavsky, who has opposed such a commission, said Tuesday that he thinks the department needs some sort of federal oversight to address "chronic structural problems."

Supervisor Mark Ridley-Thomas said he and his colleagues would move swiftly to select an interim department head who would be committed to increasing transparency and accountability until voters choose Baca's successor. Baca plans to step down at the end of the month, well before the June primary.

"The first order of business is to make sure that reform is institutionalized," Ridley-Thomas said.

At a press conference announcing his retirement, Baca insisted his jails were safe and that his reforms aimed at reducing force against inmates were in place. He recommended that the Board of Supervisors pick his head of jails, Assistant Sheriff Terri McDonald, to temporarily run the department until a permanent successor is elected.

McDonald, previously a top official for the state's prison system, joined the Sheriff's Department last year after the blue-ribbon county commission recommended hiring an outside custody expert to run the county's jails.