(Because yes, substance actually matters, not just result.)
As for electoral politics...I suspect it will not have nearly the impact folks expect, particularly desperate Rs looking for a lifeline. Culture War fades in importance in economic hard times, unless you are prepared to use scapegoating as an organizing tool and don't object to a few lynchings or pogroms. Hitler did not win on "culture war." He made a direct link between Jews, Communists, and the terrible economic situation in Germany at the time. Similarly, unless the Rs are going to find a link between the "gay agenda" and $4/gallon gas, I don't think voters outside of CA are likely to be terribly motivated by this issue.
In CA, it is a somewhat harder question. It probably does save a few Republican seats in CA, by enhancing voter turnout. But McCain can't campaign too stridently on the issue without losing support among libertarian Rs and independent who are sick of culture war taking dominance on the policy agenda.
As for the CA constitutional amendment, we'll see. There is a real irrational "ook" factor for many people raised in a generation where "alternate lifestyles" were called "perversions of nature," no matter how much they try to get past that. What would make it even more unfortunate is that CA is actually a state where the legislature has passed a same sex marriage law, albeit one vetoed by the Governor. But it was clearly only a matter of time before the political climate shifted sufficiently to make passage and signing a certainty. If the constitutional amendment passes, all that is flushed down the toilet.