San Francisco — The idea of two Californias--northern and southern--is older than the state itself.
In fact, nature fashioned a physical barrier between the two areas long before men arrived on the scene to impose their political definitions. In his 1946 book ''Southern California: An Island on the Land,'' Carey McWilliams described it: ''Southern California is rescued from the desert by the San Bernardino and San Jacinto mountains on the east and is walled off from the great Central Valley by the transverse Tehachapi Range which, running in an east-west direction, unites the Sierra Nevada and the coast ranges.''
In 1822 formal division of the state was proposed in the Mexican legislature. When the Americans who had taken over control held a consitutional convention in 1849, delegates from the southern area raised the question of formal division. Even after statehood (Sept. 9, 1850), the idea of two states was discussed--mainly by southern Californians concerned about domination by the north, where the state capital has always resided.
Today it is northern California--dwarfing the coastal south in area but not in wealth or population--that is concerned about being dominated. Southern California is the proverbial tail that wags the dog. In a state comprising 158, 693 square miles, the highly urbanized area stretching from Santa Barbara south to San Diego and eastward from Santa Monica to San Bernardino covers less than 12,000 square miles. Yet it contains more than 50 percent of California's people , jobs--and votes.
Not all of California's liberals are in the north and all the conservatives in the south. But there is no denying that the southern''island'' produces much more support for conservative causes and politicians than the north. It's a phenomenon that politicians expect. But a couple of late trends in the current primary campaign hint that it is not immutable.