John Gioia has easily regained his Contra Costa County Board of Supervisors District 1 seat, defeating challenger Hulan Barnett with 85.41% of the vote in Tuesday's election, according to the unofficial results.

Gioia first won the West County post in 1998. His district includes Richmond, San Pablo, El Cerrito, part of Pinole, and the unincorporated communities of Bayview, East Richmond Heights, El Sobrante, Kensington, Montalvin Manor, Tara Hills, North Richmond and Rollingwood.

Barnett, a Richmond resident and math teacher at Antioch's Dallas Ranch Middle School, ran a vocal campaign against Gioia, encouraging followers on social media to show up at Gioia's campaign events and "raise hell." Barnett earned 14.59% of the vote.

A vocal critic of the pandemic mask mandates -- something Gioia supported -- Barnett said his priorities were education, affordable housing, and better business development.

Gioia campaigned on his record, which he said included pushing for two county oil refineries to convert to producing clean fuels and a Richmond factory converting to producing clean hydrogen. He also touted his involvement in developing the county's affordable housing trust fund and helping more people get access to mental health and homeless services.

Meanwhile, there will likely be a runoff in November between Pleasant Hill City Councilmember Ken Carlson and BART Director Debora Allen to replace retiring District 4 Supervisor Karen Mitchoff on the Board of Supervisors.

Carlson sat in first place in Tuesday's primary election, garnering 27.13% of the vote, as of the latest results update on Friday afternoon. Allen is positioned in second, with 25.58%, according to unofficial results.

Concord City Councilmember Carlyn Obringer finished third, with 24.31%. Carrillo Garza, a former public health program manager for Contra Costa Health Services, finished fourth with 13.99%, followed by Concord City Council Member Edi Birsan with 8.99%.

District 4 includes parts of Walnut Creek, Pleasant Hill, Concord, and Clayton. As the top two finishers in a race in which no candidate finished with more than 50% of the vote, Carlson and Allen earned the right to face off in the November election if the current results hold.

The Contra Costa County Elections Division reports having about 69,000 ballots left to tabulate, the vast majority of which are vote-by-mail ballots deemed eligible by postmark by or before Election Day last Tuesday.

Editor's note: DanvilleSanRamon editor Jeremy Walsh contributed the most recent results information to this story.