PPIC is out with a new gubernatorial primary poll and it has governor getting 47% of the vote, with his closest rival, Republican Tim Donnelly, getting 10%. The undecideds are overwhelmingly Republican and independent. California has a polarized electorate. Republicans and right leaning voters vote Republican. That's why the best a Democrat has gotten since 1986 in two party vote is 62.5%. Democrats have gotten much higher percentages in states that are far less blue.
If you look deeper, Brown is getting 15% of the Republican vote, which is entirely conceivable given his image of reasonableness. But that's probably his upper limit with Republicans. I know no one knows the other candidates, but it'd be odd for the Republicans to get all the remaining Republican vote. Undecideds for a party don't usually break entirely for that party.
The electorate they used 44%D/29%R/28%O is conceivable for the general election but far less Republican than the primary electorate will be. Of course, when the Republicans are only beating Brown 29%-15% with Republicans you're not going to change the results much even with a more Republican electorate. I'm now thinking that Brown (and the other Democrat) beat the Republicans 53%-41% in June. Donnelly seems very likely to finish second, mostly because I don't know how Kashkari becomes well known enough to beat him.