More believable than him only being up 4 (lol), but I'm guessing Newsom will still win by more than this.
https://projects.fivethirtyeight.com/polls/governor/california/
You can see some distinct trends here. Optimus is a C- pollster by itself (Thomas Partners/Optimus is unrated). But whether you leave it in or filter it out and say only show B and above pollsters, you have enough data to see that Cox will at least do a fair amount better than Trump '16 margin. He seems to be stuck around 40% in the average though. So the presidential '16 numbers might actually be a good indicator for this race. Because of the Top 2 system, there won't be any third party bleeding like there was in the '16 presidential race, so Newsom might just match Clinton's 61% leaving Cox with 39%. Give or take a percentage point or two from either candidate.
Eh, no 3rd party bleeding just means people like me will abstain.
