I imagine that amendments declaring marriage to be a one-man, one-woman affair would pass in most states, but I’m not sure how much of a bellwether Missouri is on this issue. I’ve always had the impression that it was more socially conservative than your median state, and that its Democratic voters (many of them rural) were more socially conservative than their counterparts in many states.
As for whether the FMA will “take off like a rocket,” as Stanley suggests: Senator John Cornyn, interestingly, tells Terry Eastland that the FMA will be enacted only when courts make more rulings in favor of same-sex marriage. In particular, he thinks that federal-court decisions that struck down the Defense of Marriage Act or imposed same-sex marriage on a state would cause it to be enacted.
Such decisions, at least if made in the next year or so, would increase the likelihood of enactment. If you were a legal activist working for same-sex marriage, or a judge looking to promote the same cause, the cautious thing to do would be to avoid seeking or issuing those decisions. Concentrate on the state courts, where there have already been successes. Get same-sex marriage imposed on several states and hope that it becomes normalized and opposition softens. Wait a few more years before moving to the federal courts, so that when the federal courts do move there will be less chance of a backlash.
I think that would be the most prudent strategy. But then, I thought last fall that the Massachusetts court would better advance the cause of same-sex marriage by settling for civil unions for the moment. I’m less confident of that judgment now, but in any case it did not help to predict what the court would actually do.