The cable news media (and Sanders supporters) have been crowing that the California Democratic primary is very close. But they are only looking at one poll -- the PPIC poll. There have actually been four polls -- two of them have the race as close, and the other two show Clinton with a substantial lead. The RealClearPolitics Average (which I tend to believe over any individual poll) has Clinton with a lead of 8.7 points.
The polls shown are:
Fox News Poll (4/18-4/21) 623 likely voters (4.0 point moe)
Hoover / Golden State Poll (5/4-16) 694 likely voters (no moe)
Public Policy Institute of California Poll (5/13-22) 552 likely voters (5.7 point moe)
KABD / SurveyUSA Poll (5/19-22) 803 likely voters (3.5 point moe)
I think Clinton will probably win California, but it really doesn't matter. By the time California polls close, New Jersey will already have given her enough delegates to clinch the nomination -- and no matter who wins, Clinton will come out of California with over 200 more delegates (which will just pad her winning delegate total).