Mr. Horsley, an Emerald Hills resident who was a longtime sheriff of San Mateo County, received 78.5 percent of the vote. The count on election night was 14,805 for Mr. Horsley and 4,048 for his challenger, Michael Stogner.
District 3 includes Atherton, Portola Valley, Woodside, parts of Menlo Park and Belmont, San Carlos, and large coastal and unincorporated areas.
Michael Stogner, a San Carlos businessman and victim's advocate, ran against Mr. Horsley in 2010, and ran for the District 1 seat in 2011. He has never held public office, but has gained attention in the county as a government watchdog.
This is the first by-district supervisor race, which means only residents of District 3 can choose the district representative.
In a recent interview, Mr. Horsley told the Almanac that during a second term, priorities would include upgrading farmworker housing, which would improve the lives of many migrant workers "who really aren't migrant anymore" but whose presence is critical to the county's agricultural sector; improving facilities and services of the Cordilleras Mental Health Center in unincorporated Redwood City to "help the mentally ill people (served) there deal with their illness and be reunited with their families"; and traffic management on the Coastside.
He said he will also continue to work on resolving traffic problems for bicyclists, pedestrians and motorists on Alpine Road in the South County.