Gonna WIN IT BIG! I'm gonna say six points.
The polls of likely voters may say that, but the logistics of independents voting for Sanders on election day will wipe that out. We have a LOT of non-affiliated voters in California.
The latest voter registration figures:
44.82% Democrat
27.29% Republican
2.55% American Independent
0.43% Green
0.64% Libertarian
0.40% Peace & Freedom
0.55% Other
23.32% non-affiliated
The Democrats let non-affiliated voters vote in their primary, but they have to ask for a Democratic ballot. They do NOT let those registered for any other party vote in it. But the real problem is that 64.9% of the ballots in the last primary were cast by mail. If you want to get a Democratic primary ballot by mail, you had to do that some number of weeks ago. You can't just wait until this week to open your mail ballot and still have time to do that.
Even if that 23.32% of voters all show up at the polls and ask for Democratic ballots, are they going to have that many spare ballots at each polling place?
So I think you have to apply a pretty big discount to the number of non-affiliated and non-Democratic Party voters who intended to vote for Sanders. And I bet those people who are Democratic Party registered heavily favor the actual Democratic in the race.
