LOS ANGELES – Mayor Eric Garcetti will endorse Long Beach Police Chief Jim McDonnell for Los Angeles County sheriff, his office announced tdoday.

Garcetti is set appear Tuesday with the longtime former LAPD officer — he was second in command to former chief Bill Bratton until he was hired in Long Beach in 2010 — on the steps of City Hall to lend his support to McDonnell in the Nov. 4 runoff against former Undersheriff Paul Tanaka.

McDonnell, 54, was the only outsider among the seven candidates who battled earlier this year to take on the task of overhauling the Los Angeles County Sheriff’s Department, which has been under fire over the treatment of inmates — leading to federal indictments and the retirement of Sheriff Lee Baca.

Baca, a four-term sheriff, retired in January.

Eighteen sheriff’s deputies were indicted in an ongoing federal investigation that has implicated at least two additional deputies to date.

Baca’s surprise departure cleared the field for others, including McDonnell.

McDonnell has endorsements from the Los Angeles Times, the Los Angeles Daily News, District Attorney Jackie Lacey, LAPD Chief Charlie Beck, City Attorney Mike Feuer and state Attorney General Kamala Harris.

He also has the backing of four of the five county supervisors who control the department’s budget: Michael Antonovich, Gloria Molina, Zev Yaroslavsky and Don Knabe, who appointed McDonnell to serve on the Citizens’ Commission on Jail Violence in 2011. Tanaka has been mostly silent since the primary