This will not mean much outside of the Western megalopolis but it's breaking news here. Richard Riordan, conservative Republican mayor of LA, during the turbulent '90s, is announcing his support of Barack Obama for President. Riordan is a member of and influential with, the big donor, old money, social elite of Southern California. This will not be so much a boost to Obama but rather a loss of legitimacy for the McCain candidacy among the moneyed, fiscally conservative class in SoCal.
The social register types in SoCal tend to be miles more progressive on social issues than what you find in most areas. They are notably pro choice and gay friendly. It is not likely they have fallen under the spell of 'hivehead Sarey Paleface and her tongue talking, meth spiking, little brood of offal-spring.
The other thing notable about this endorsement, is that Riordan won election twice, because of heavy Hispanic support. They voted for him because of his staunch Catholicism and alliance with the Church, as much as for his unqualified support of high quality education and keeping of the peace, even in the poorest Fort Apache, areas. Anything that helps Obama with the Hispanic vote in SoCal, could have real significance. There continues to be a strong antipathy between the African American and Hispanic communities here, where they share many of the same, previously all black, ghettos. Riordan is also popular with the middle class to upscale suburban denizens of the vast San Fernando Valley, by virtue of his quick response and unwavering aid to them, during the Northridge quake, a natural disaster that rivaled Katrina, in it's devastation and displacement of the populace there.
California won't win you the Presidency but it's a damn big step stool to stand on.