According to the secretary of state, about 80% of ballots in California were cast by mail last year in the general election.

Election officials, state attorneys general and legal experts say President Donald Trump's executive order seeking to reshape election processes throughout the U.S. will likely face legal challenges for violating the Constitution.

President Donald Trump on Tuesday signed a sweeping executive action to overhaul elections in the U.S., including requiring documentary proof of citizenship to register to vote in federal elections and demanding that all ballots be received by Election Day.