I'm not necessarily recommending this, but...
...if the constituents in the Republican party in California were interested in overturning Proposition 8 (which outlawed Gay marriage) they would make the battle entirely a referendum on the main sponsors of the amendment, the Mormon Church of Latter Day Saints.
They would sponsor an alternative amendment entitled something like the "California Constitution and Self-Determination Act" and run ads that talked about an "outside religious group from Utah, with radical views such as polygamy, invested millions of dollars to change California's constitution in their image."
They would then go out of their way to highlight every "scary" and "out of the mainstream" aspect of the Mormon religion... the "special underwear"... "the golden tablets"... "the anti-traditional-religion bent, which contradicts the bible" and suggest this "cult" had come into "our state" in the hopes of making it more hospitable for them.
The Republicans would then try to conjure an image of mass migration of outsiders and ask, with ominous music, "are we really ready for California to become home to religious fanatics who don't share our values?"
Given the way Proposition 8 was passed, with images of downtrodden children being subjected to the "gay agenda" (and the tacit suggestion that rejecting Proposition 8 would force first-graders to watch gay-porn in class), turn-about might be fair play.
Now, the significant downside of this methodology is that it completely sidesteps the VERY REAL ISSUE that civil-unions are nothing more than the separate-but-equal, "colored water fountains" of marriage and at some point... and I think its now... we have to have a big bloody fight, mirroring the marches on Selma that establish, once and for all, that gay-rights are nothing more radical than CIVIL RIGHTS.
The significant UPSIDE to running a Republican campaign focused on the "Mormons" instead of "marriage"... it very well might work, pitting the very constituents that were convinced to cross over to support proposition 8 against its creators.
And at this point, I MIGHT settle for "work" if the alternative is California's version of anti-miscegenation laws for gay men and women.