Vote centers have been open for four hours already, and many people showed up to drop off or cast their ballots for the District Four special election.
Final day to vote in Special Election for Fourth District Supervisor - kusi.com - get the latest breaking news, showbiz & celebrity photos, sport news & rumours, viral videos and top stories from kusi.com Daily Mail and Mail on Sunday newspapers.
Polls close at 8 p.m., but official election results could take weeks. Should no candidate win a majority once all votes are counted, the top two will advance to a November runoff.
Tuesday is the final day to vote in the election to fill the vacant seat in San Diego County's Fourth Supervisorial District following former supervisor Nathan.