It could take weeks - or even a month - before we know who won elections in California and Los Angeles.
Another Democrat, billionaire climate activist Tom Steyer, is in third place as the tally continues.
California, Iowa, New Jersey, New Mexico, Montana and South Dakota held key primaries on Tuesday.
California could have its first Republican governor since Arnold Schwarzenegger ended his two terms in 2011.
Voters in six US states are casting primary ballots that will set the battle lines for November's midterm elections.
US gov't cuts to food stamps will hit thousands of Californians. The state is set to vote on billionaire tax to make up.