Given the data put together by Nate that is currently linked on the front page here, I would say there's one obvious new question to put to opponents of gay marriage:
"Are you willing to ban gay marriage even if, as research has revealed, this actually also has a negative effect on heterosexual marriages?"
I, for one, hope that the plaintiff's lawyers in the Prop 8 case find some way to introduce this new data into evidence.
But here's another question which never occurred to me before, which I hope someone in the media will ask of the right person at the right time. I would like to see a man who is married asked, "Do you love your wife?", followed up by, "If, just before you were married, you had found out that your wife could not bear children, would you have cancelled the marriage?" and then, lastly, followed by, "What if the government said that people who are not capable of bearing children cannot be allowed to be married?" Because based on all their arguments, that would be consistent. I have seen the last question posed before, but never in the personal context in which the leading two questions would place it.
Lastly, I would like to see someone arguing the case on openly religious grounds asked the following. "You are a Baptist. Suppose that the push to introduce more religion into our government were to lead to a Catholic takeover of the government, and a law was passed saying only Catholics could get married. Would you convert?"
This is not as absurd a question as it seems, to anyone who knows their history. It was only a few hundred years ago that such situations existed in the world.