I could easily see Trump losing Cali 65-35, and possibly even worse.
This guy is just about the worst fit I could imagine for a Republican GE candidate in the state. Sure he might gain a few extra points in some small rural counties in the northern part of the state, and maybe even grab one or two Sanders voters here or there, but he's not going to do well with Fiorina and Whitman Republicans in most parts of the state, combined with what looks well like will be huge Latino voter turnout numbers in November, including a ton of first-time voters that registered to vote since January, heavily motivated by the disturbing and racially charged comments against Latino Americans.
Key question will many of these new voters go down-ballot and put CDs in places like the (3) CDs in Central Valley and several others in North Coast San Diego/SoCal into play and pad the already overwhelmingly Dem congressional delegation margins.
It'll be very interesting to see if he puts his money where his mouth is and contests the state. A man can dream...