Is Calif an open primary? If so, you could see Democrats jumping in big time to determine the nominee.
It has a semi-open primary. Registered voters who have chosen "Decline to State" as their party may select a SINGLE party's partisan-primary ballot. (Of course, registered party members also can vote in their own party's primary.) Voters who are registered in another party cannot vote in the Republican primary.
Of course, any approach allows for mischief. Anyone may REGISTER IN any party at all, with little waiting period and no means of weeding out "Operation Whatever" clowns.
It's a closed primary with delegates awarded proportionally by Congressional District. 3 per each of the 53 districts and about a dozen at-large delegates.
Newt has been campaigning hard here.