So far that means only military and overseas voters, but county elections officials will begin sending ballots to everyone else on Monday.
Voting by mail has become increasingly popular in California. A record was set in the May 19, 2009 statewide special election with 62.2 percent of voters casting their ballots by mail, according to the Secretary of State's office.
Voting by mail is open to anyone, and the last day to request a ballot is May 29. You can request one here.
The last day to register to vote and still be eligible for the primary is May 21. The Secretary of State accepts online voter registration now.