I just had a thought. While recent gay marriages in San Fransico and New Mexico have energized the anti-gay marriage fundamentalists they may ultimately be the cover that moderates need to vote against the Federal Marriage Amendment. If we look at the polls we see the country is fairly evenly split on the issue of gay marriage with the advantage going to the anti-gay marriage side.
However we need to remember that fundamentalist are only 15% or so of the population. That other 35-40% who oppose gay marriage are not so extreme. Driving a wedge between them and the fundamentalists shouldn't be too difficult.
The issue that needs to be raised is what will happen to the thousands of gays who are already married? This FMA needs to be cast as the biggest divorce in history. Many of those near the middle who oppose gay marriage may be hard pressed to agree to government mandated divorces.
Those divorces can become the shield nervous moderates need. When the fundies scream about how so and so voted against the FMA they can respond by talking about divorce and how it is wrong to force people to get divorced.