This report is a little confusing--mostly because it was written at a couple different times throughout the day--but it sounds like the California chapter of the service employees union, SEIU, is endorsing Obama today. Combine that with the Kennedy endorsement, the recent endorsements by members of the California congressional delegation, Obama's unprecedented organization in the state, and the fact that independents can only vote in California's Democratic primary, and the fundamentals continue to improve for Obama there.
Having said that, I think he's still a pretty long shot to win the state, mostly because a significant number of people (maybe 20-25 percent) have already voted in California, and they favored Hillary by a wide margin. As Daily Kos diarist Poblano has pointed out, that means Obama would need to win a significant majority of the remaining votes to come out ahead overall. My gut says he'll get to 45 percent, but probably not 50. (Though that could obviously change with something like a Gore endorsement...)
Update: A friend who's very knowledgeable about California politics writes:
[I]t’s important to remember that the absentee vote in California is far older and whiter – but with fewer professionals making more than $100k – than the election-day voter.
In other words, it matches up with the demographics of Hillary’s existing support almost perfectly. Those early absentee voters would have been in Hillary’s camp regardless of any Obama surge; absentee voting just lets them mail in the foregone result sooner.
I suspect that the people who are left – younger, non-white, and professional voters – are all Obama people, and so her lead isn’t quite as invincible as it seems. (The exception to this trend is, of course, Latino voters, but ... Hillary is NOT going to win Latinos by the 25 or 30 points the polls suggest – those polls are totally a function of name ID, and you already see the gap rapidly closing in the last few days as the ads go up on TV and radio.)
Right now, I’d say the state is a toss-up, and it’ll depend on who does a real ad buy over the weekend. And I think this is why Hillary has basically parked herself in the state today and tomorrow: she knows CA is way more close than it seems, and a loss here would be pretty devastating to her perceived front-runner status, regardless of the delegate split.