The true split would be into East and West the lenght of the State.
West = Liberal; East = Conservative.
In The Nine Nations of North America, the author ran the dividing line from somewhere around Santa Barbara up into British Columbia. Very distinctive coastal culture: outdoorsy, nonintellectual, Lefty-trendy, wine-slurpie brie-eaters. East of that is the Mountain West, very conservative and American. Below Santa Barbara he consigned to "Mexifornia" .... might be why Oprah and other moguls perch in Santa Barbara, it's the closest real estate to their offices that is actually part of the United States!
Hard to say where Palm Springs fits in.