Uh . . . that would probably include the party that has a lot of evangelical Christians.
I'm unfamiliar with California demographics but I always thought an evangelical was a term generally applied to certain Protestant groups. I also understood that most large Protestant groups do not forbid contraception wheras Catholics do. As a result, Protestants will tend to have lower birth rates than their Catholic counterparts.
I also understand Mormons do not allow contraception either. Therefore Mormons like Catholics would tend to benefit.
Ultimately, the party with higher birthrates will benefit the most.