The assertion came as Republican presidential nominee Donald Trump repeatedly claims the election is rigged in favor of Democratic nominee Hillary Clinton.
Jesse Melgar, a spokesman for the California secretary of state, says double voting in California is rare.
Dean Logan, president of the California Association of Clerks and Election Officials, adds that registrars regularly update voter lists and remove dead people from the rolls.
Data tracking company Political Data Inc. expects voter registration in California to hit a record 19.4 million for Tuesday's election.
More than 3.3 million ballots have already been cast in early voting, according to the company.
CapRadio provides a trusted source of news because of you. As a nonprofit organization, donations from people like you sustain the journalism that allows us to discover stories that are important to our audience. If you believe in what we do and support our mission, please donate today.