It appears there'll be eight member v. member congressional races in California. In two of them, CA-40 and CA-43, the incumbent isn't facing serious competition and there aren't a lot of Republicans. CA-44 is the Hahn-Richardson match-up, but Democrats outnumber Republicans there 5 to 1. So they likely won't matter much.
There are five districts where The other party matters.
CA-15 - Pete Stark v. Eric Swalwell. Tea Party member Chris Pareja ran as an NPP. That may have cost him advancing. Republican turn-out was high and they may have been as much as 30% of the electorate. By running NPP, however, Pareja didn't give Republicans any reason to think his ideology was similar to theirs. The district is 48%D/23%R/29%I. If Swalwell runs a good campaign Stark is done. If he takes 20% of Democrats, which he should do easily, he'll get enough Republicans and independents to win. Stark has doubled down on his far left positions, although it's not like Republicans didn't oppose him before this. All Swalwell needs to do is to tell Republicans he doesn't hate business, his door is open to them, and that he's sane unlike Stark. I could easily see Stark remaining in the low 40's.
CA-35 - Joe Baca v. Gloria Negrete McLeod. Green Party member Anthony Vieyra got 19%. He should be to the left of those two. This district is 27% Republican.
CA-30 - Howard Berman v. Brad Sherman. There's a good share of Republicans here too, but they totaled only 22% of the vote when the electorate was over 30% Republican. I assume Berman got many of those Republicans, as he has more Republican endorsements. So he should keep doing what he's doing. I can't wait for Howard Berman and Brad Sherman talking to the San Fernando Valley Republican Club.
CA-8 - The final two are unknown, but it appears to be Greg Imus and State Assemblyman Paul Cook. The district is 32% Democratic. Imus may have trouble appealing to this group, as he's known for his hardline stance on immigration. He may not even try to appeal to Democrats, thinking the district is Republican. That'll be a big mistake. Paul Cook will make him look like he's fringe and will win easily.
CA-31 - Since this district is 41% Democratic, Republicans Gary Miller and Bob Dutton are in an odd position of having more other party voters to appeal to.
All of these candidates should avoid trying to pander to the other party by changing their positions. They'd appear to be a flip-flopper who'll say anything to win an election. They'll lose the votes they have from their own party while chasing people who don't want to vote for you and who won't trust you. They could just as easily leave the ballot blank rather than vote for someone they don't want to see elected. They should emphasize positions that might get them other party votes, but they should sell themselves and not their positions. It doesn't hurt if your opponent can be perceived as extreme and hostile. That strategy will likely work for Swalwell and probably also for Cook.