Yeah, I'm not sure who this counts as good news for though. Clinton is technically ahead (good for Bernie) but it's also the tightest California poll yet (good for Hillary).
In the old days, ARG was always the least accurate poll, so Clinton +1 would mean that Clinton would win by a big margin, since all the other polls have her doing better. It wasn't that ARG always got the winner wrong. It was that they were always the farthest off from the real result.
However, in recent years, ARG is just a bad pollster. They're as likely to be close as they are to be way off, as their numbers just seem to be random.
