Gay marriage wasn't on the table in California in 2004, but it was in other states to the benefit of Republicans.
It may help in statewide elections, such as Governor and Lt. Gov., but it won't make a spit's worth of difference in who wins on a district by district basis. The districts are carved out exquisitely along party lines to benefit incumbents with overwhelming local majorities.
The state legislature is unafraid of defying public will of 70% of the population because they know they have job security. Jackie Goldberg could introduce a bill to to make wearing buttless leather chaps mandatory, and get reelected with an overwhelming majority.