"I think I'm more closely aligned with Bobby philosophically," Duran said. As an example, he pointed to their shared desire to amend the California Environmental Quality Act to loosen regulations on developers.
"I am honored to have John’s support," Shriver said in a statement. "We see county government the same way: Sound fiscal management is key."
The endorsement is significant because Duran captured 16 percent of the vote. Shriver, 60, the nephew of President John Kennedy and former mayor of Santa Monica, finished second in the primary to former State Senator Sheila Kuehl.
Kuehl beat Shriver 36-29 percent in the primary.
Kuehl, 73, is seeking to become the first openly gay member of the county board, which oversees a $26 billion budget and a wide array of services including the foster care system and public hospitals.
Duran is also gay, so his support could help Shriver win support in that community as he seeks to succeed longtime Supervisor Zev Yaroslavsky. He is termed out in December.
Kuehl said she was “disappointed” in Duran's decision.
“It’s quite disloyal to the LGBT community,” she said. "I don’t think every gay person has to endorse every other gay person but if you have a qualified LGBT candidate, you’d think you’d take that into account.”
"I did not want to make my decision based on sexual orientation," said Duran, a longtime gay rights activist. He noted more gays and lesbians than ever serve as elected officials. "I think we are beyond the part of electing the first of everything."
Kuehl noted Congressman Brad Sherman and Los Angeles City Attorney Mike Feuer endorsed her recently. “I think those endorsements carry more weight,” she said.
Duran had his own powerful support during the primary. LA Mayor Eric Garcetti and the Los Angeles Times endorsed him. Garcetti has yet to endorse in the runoff.
While Duran’s backing may be helpful to Shriver, Yaroslavsky’s endorsement is the most coveted. A spokesman would only say he’s “left the door open” to picking a preferred successor.
The Third District supervisor represents an area that stretches from Malibu through Santa Monica to Hollywood, and encompasses the entire San Fernando Valley.