POD 1990, make it happen. No ideological adjustments allowed in either party except for some leeway (by which I mean somewhere in between SB 1070 and DREAM, no amnesty allowed) on immigration for the GOP. Double Bonus if CA becomes solid Republican (like the Deep South) by 2012. Triple Bonus if Republicans fill all major statewide offices (governor, AG, both senators) by 2012.
To make it easier if you want, a POD of 1985. The Cold War must end on schedule.
My suggestions: work with white flight as a starting point.