I live near OC and Republican turnout was very low due to unpopularity with Trump. Hispanics make up a large portion of the county and as stated many times, they had a large turnout. The Hillary vote was overwhelmingly coming from Santa Ana and parts of Anaheim. I believe this was a one time thing. What I'm curious is if other CA counties will be DEM strongholds in future elections like Fresno, San Diego, and other CA counties that tilt blue.
Orange and San Diego seem like the most immediate concerns for California Republicans. If the Republicans think they've hit rock bottom in California, then they're in for a world of hurt because there's A LOT of room left to fall in Congressional and legislative numbers in those two counties alone. Trump held up surprisingly well in Fresno and Riverside, if it's any consolation. He barely did any worse than Romney there, so just MAYBE those counties' trends have stopped, though it's still too soon to tell. But yeah, Orange County in particular has the potential to be absolute hell for Republicans over the next four to eight years, and after that, it might be too late for them to reverse the damage. This will probably also play out to a similar extent in Maricopa, Gwinnett, Cobb, Fort Bend, and other counties like it.
It is a concern for Republicans, indeed. I still think the OC thing was a one time Trump thing but
I may be wrong. And yes, I agree that Democrats could go after some more traditionally Republican counties like Kern,Madera, Tulare, etc. The only solid Republican counties left in the state are the ones in the far north like Modoc and Lassen. Trump got around 70% of the vote up there.