It's easy for political analysts to talk about "the Latino vote" as if 15 million people in California all shared exactly the same views and cared about exactly the same issues. Which is nuts: Latino voters are a diverse group.
On the other hand, it's safe to say that over the past 15 years or so, as the California Republican party has become more and more viciously anti-immigrant, Latinos have been rejecting GOP candidates. When Pete Wilson pushed Proposition 187 -- which would have prevented undocumented Californians from receiving public health services and would have kicked their kids out of public schools -- he wrote off an entire generation of Latino voters.
And Jerry Brown has a strong history of supporting causes that resonate with a lot of Latinos.
So in general, recognizing that not all Latinos remember Brown's support for Cesar Chavez or cae about the creation of the Agricultural Labor Relations Board, it ought to be a good assumption that Brown will win the Latino vote by a pretty wide margin. The fact that Whitman is narrowing his lead among Latinos is, I think, a sign that Brown is resting too much on history and hasn't offered much in the way of ideas about jobs, education, or any of the other crucial issues that middle-class voters of all ethnic groups care about.
Still, the Spanish language billboards were really dumb. For a campaign that's been as disciplined and message driven as the Whitman effort, it's kind of a surprise. All Meg has done is give Brown a nice weapon, a reason to talk about an area where she's very weak. And the more he can keep playing on that -- the more he can point out how far to the right she and her advisors really are on immigration -- the more it hurts her.