California Strategery: talk up Green Party. Bitch and moan in Birkenstock stores and Bay Area coffee houses about Boxer being a "sellout to the Oil and War Party." (If you can suggest that she's an Israeli sock puppet in a PC manner, so much the better.)
I agree Boxer could be vulnerable from her right and her left.
Davis won on LA and SF. Boxer may not have much to offer the libs -- the California economy will lag the rest of the nation and liberals, with extended 100% power, will be left holding the bag.
California Republicans have had scant success finding good statewide candidates though.