From the Public Policy Institute of California, a nonpartisan research and data organization.

*****

Voter registration is up since the last gubernatorial primary; major party registration is down.

California’s 17.7 million voters constitute 73.3% of eligible adults, up slightly from 72.4% in 2010, the last gubernatorial primary year. The share of Democrats is 43.4%, down from 44.5% in 2010. The share of Republicans has also declined from 30.8% in 2010 to 28.4% in 2014. The share of voters who say they are independent (also known as "decline to state” or "no party preference”) is 21.2%, up from 20.2% in 2010. Our surveys indicate that among those we consider most likely to vote, 44% are Democrats, 32% are Republicans, and 19% are independents.

Independent likely voters continue to lean Democratic; partisans are ideologically divided.

More independent likely voters continue to say they lean more toward the Democratic Party (38% in 2010, 41% today) than toward the Republican Party (30% in 2010, 29% today); 30% do not lean toward either major party (32% in 2010). Ideologically, Republicans are more cohesive than Democrats: slightly more than half (55%) of Democratic likely voters describe themselves as liberal, while 69% of Republican likely voters say they are conservative. Independent likely voters are more likely to be middle-of-the-road (39%) than conservative (33%) or liberal (28%). Among independents who lean toward neither major party, 15% are liberal, 53% are moderate, and 32% are conservative. Among those who lean Democratic, 54% are liberal; most who lean toward the Republican Party are conservative (64%). One of areas in which ideological divisions are most evident is taxation and spending: 63% of Democrats would prefer to pay higher taxes and have a state government that provides more services, while 79% of Republicans prefer lower taxes and fewer services; independents have a slight preference for lower taxes and fewer services (51% to 44%).

*****

So we are slowly becoming a state of independent and small party voters as people leave both main parties. It is true that more are leaving the Republican Party than the Democratic Party, but the difference is small.

But if one party outnumbers the other by more than three to two you can't expect to win many statewide elections. Of course you can do better in local elections, but the Republicans now don't have a majority in any county of California. Both parties now have to appeal to the middle. This is much more important now that the party in power (or an agreement between the parties as in the last redistricting) can no longer gerrymander the state.

The top two finishers, regardless of party, running in the general election (as voted for by the people) also encourages centrism, as was its intent.

There are plenty of "baggers" in California. They live in the poorest counties. I know that makes no sense from a political science point of view, but it is true just the same.