Watch the Democrats steal the election in San Francisco.
Compared to the rest of the state San Francisco is relatively small. Moreover, they already vote 70-80% rat most of the time any way, so even if they were to flip every Republican vote in their county, it wouldn't make too big of a difference.
I'd be more worried about the lefty registrars and bureaucrats in the conservative leaning or marginal counties like San Bernardino, Fresno and Sacramento. LA despite its massive size and liberal slant, actually has a very well run registrar. I've spent many horrible November weeks there napping in hallways, though not recently.