Nate Silver On Marriage Support Trends
For right now, it is probably best to treat the question of whether a majority of Americans support same-sex marriage as having an ambiguous answer. Polls are on the verge of saying that they do, but the ballot results are more equivocal. By 2016, however, voters in 32 states would be willing to vote in support of same-sex marriage, according to the model. And by 2020, voters in 44 states would do so, assuming that same-sex marriage continues to gain support at roughly its previous rate.
Thus, even if one prudently assumes that support for same-sex marriage is increasing at a linear rather than accelerated pace, and that same-sex marriage will not perform quite as well at the ballot booth as in national polls of all adults, the steady increase in support is soon likely to outweigh all other factors. In fact, even if the Supreme Court decision or some other contingency freezes opinion among current voters, support for same-sex marriage would continue to increase based on generational turnover, probably enough that it would narrowly win a national ballot referendum by 2016.