CA's problem areas are mostly a few coastal areas - my home Silicon Valley being in one such - and the Sacramento-Davis area (gooberment types and a UC; but not so much Woodland or Dixon). Those are also some of CA's most populous areas.
I have to admit I'm not an expert on the lay of the land out there.
I traveled there extensively through the 90's and 2000's and noted that the folks in the Northern half were not much different at all than those where I come from ideologically. But when I was in the lower part of the state, Livermore, SF, LA, Tustin... it was left-wing nut territory. I didn't get out much though, mostly work and a little beach time when I could fit in an hour or two.
Seems like it's the typical urban v/s rural situation, only that Southern CA is almost all urban and that ruins it completely.