Ending the marriage of a Democratic power couple after a sordid public breakup, California Treasurer Bill Lockyer has filed for divorce from former Alameda County Supervisor Nadia Lockyer, who had an affair and has struggled with a drug abuse problem in recent months.

The divorce papers, filed Friday in Alameda County Superior Court, cite "irreconcilable differences" between the 71-year-old California political institution and his 41-year-old wife.

Tom Dresslar, Bill Lockyer's spokesman, said Monday afternoon that "Bill's desire is to above all resolve the matter in a way that serves'' the best interests of the couple's 9-year-old son Diego.

"Beyond that, he wants to the extent possible for this to be handled as privately and as amicably as possible," Dresslar said.

Shortly after the court filing, Nadia Lockyer, was injured in a solo car accident.

At about 5:10 p.m. Friday, she was talking on her cell phone when she veered off the road while driving in her Hayward Hills neighborhood, hitting a light pole and a tree, Hayward Police Sgt. Eric Krimm said Monday.

Krimm said her car's air bag deployed, but she suffered some facial cuts and complained of pain in her arm and was taken to a hospital by ambulance; she was not seriously injured.

Alcohol wasn't a factor in the crash, Krimm said, and Lockyer was alone in the car when it happened. Police aren't sure how fast she was driving but Krimm said she made an "unsafe

turning movement" before the crash. She wasn't cited or arrested.

Neither Nadia Lockyer nor Bruce Jobson, Bill Lockyer's attorney, immediately responded to emails and phone calls Monday seeking comment about the divorce filing.

When she resigned in late April, Nadia Lockyer told this newspaper she was determined to fix her crumbling marriage.

"We're married. There's no talk of changing that, " she said. "We're committed to our son."

Trouble between the Lockyers surfaced in February after Nadia Lockyer told police that the lover she had met in a chemical-dependency program had attacked her in a Newark hotel room. But the state Justice Department investigated and in April declined to charge him with any crime. For weeks, the tempestuous affair between Nadia Lockyer and Stephen Chikhani -- a 35-year-old convicted felon from San Jose -- unravelled in the media through a series of text messages, secret recordings and rumors of a sex tape.

Nadia Lockyer resigned her seat on the board of supervisors in late April, months after the Chikhani incident brought her affair and her drug addiction into the public eye.

The Lockyers had wed in 2003, in what one veteran political operative at the time had called "a match made in political heaven."

By the time Bill Lockyer met Nadia Maria Davis about a decade ago, he was a Democratic political giant serving as California's attorney general after 25 years in the Legislature. Twice married earlier in life, he'd long been a bachelor.

Her father had been a renowned immigrant-rights lawyer, and she had cut her political teeth in Orange County by working on campaigns and winning a four-year term on the Santa Ana Unified School District board. When they met, she was four years younger than Bill Lockyer's daughter from one of his previous marriages.

The Lockyers, who have shared a home in the Hayward hills, became a prominent Democratic "power couple" from whom many local candidates sought blessings and support. Bill Lockyer transferred about $1.5 million from his campaign committee to his wife's 2010 campaign for supervisor, allowing her to swamp her rivals in a blizzard of direct mail and advertising.

In an extended interview with this newspaper to announce her resignation, Nadia Lockyer declared her commitment to focus on her recovery from addiction and her family. She thanked her husband for "his incredible patience and love and understanding despite the things I shared about past hurts and losses.

"I'll never feel I can do it enough,'' she said.

Staff Writer Julia Prodis Sulek contributed to this report. Josh Richman covers politics. Follow him at Twitter.com/josh_richman. Read the Political Blotter at IBAbuzz.com/politics.