Spending by outside groups made last year's race between Susan Gorin and John Sawyer for the 1st District Sonoma County supervisor's seat the most expensive in county history, campaign finance reports show.
Gorin, Sawyer and independent groups reported spending $826,400, topping by $1,600 the 2010 mark set in the 2nd District supervisor's race between David Rabbitt and Pam Torliatt.
The new record marks the third time in four years that a new spending high has been reached in a county race. The trend has played out during a generational turnover on the Board of Supervisors.
The high-stakes battles for those open seats are increasingly being waged by outside groups, which operate under far fewer campaign finance restraints than candidates.
Around the state, the number of independent campaigns operating in county races has multiplied as elected officials leave term-limited higher office or lower-paying city seats for county office, experts say.
"The county supervisor gig is the best political job in California," said David McCuan, a Sonoma State University political scientist. "That's going to drive dollars to both the candidates and the outside groups."
Another contributing factor is the quick rise in the county's allowable maximum direct contribution to candidates. It has more than doubled since 2008, to a limit last year of $2,625 in any reporting period, or $5,250 in any period once independent spending reached $10,000.
Expenditures by outside groups accounted for about $219,000 of the spending in the Gorin-Sawyer race, featuring two longtime rivals on the Santa Rosa City Council.
Groups favoring Sawyer were financed primarily by real estate and business interests. They spent $142,000, mostly on advertising, according to campaign records released last week.
A coalition backing Gorin and supported primarily by the county's largest public employee labor union reported spending $77,000 on the race.