Twenty-nine states have constitutional amendments defining marriage as a heterosexual union, but voters in as few as two would absolutely approve one today, according to new analysis published in The New York Times on Tuesday.

Statistician Nate Silver's predictions on the percentage of the vote such a ballot initiative would receive is based on 34 nationwide ballot initiatives.

Silver works the numbers from several angles; looking at amendments that ban all forms of recognition and those that only seek to ban gay marriage, and applying different rates of increasing approval for gay and lesbian unions.

In one of the four models – an amendment that bans all forms of recognition coupled with an accelerated rate of acceptance for gay unions – only voters in two states, Alabama (61.3%) and Mississippi (65.7%), would definitely approve a ballot initiative in 2012. Such an initiative is also favored to win in another 13 states, including Utah (50.2%), Kansas (51.2%), West Virginia (51.7%), Texas (52.5%), North Dakota (52.7%), Kentucky (53%), North Carolina (53.5%), Georgia (53.6%), Oklahoma (56.1%), Arkansas (58.2%), South Carolina (58.7%), Tennessee (58.7%), Louisiana (58.8%).

That is, thirty-three states plus the District of Columbia would likely reject such a ballot initiative in 2012.

That number, however, plummets to 15 when a more modest linear rate of approval is applied and the amendment only bans gay marriage.

For the record, Silver writes that the accelerated model “most accurately reflects current sentiment about marriage.”

The two states where voters are likely to see such a question next year fare very differently.

A proposed amendment in Minnesota, which only seeks to ban gay marriage, would likely fail under the accelerated rate but likely pass under the linear rate. However, both models predict likely passage for an anticipated amendment in North Carolina, which is expected to bar all forms of recognition.

Silver concludes: “The future of same-sex marriage looks to be reasonably bright. Most of the states that were fertile ground for passing a constitutional ban on it did so long ago. Minnesota and North Carolina are potential exceptions, but the six states that have gender-neutral marriage laws on the books now are unlikely to see them reversed, while some of those that don't are in a position for gay rights advocates to go on offense.”

We would add that the outlook for a federal amendment banning gay marriage looks rather dim.