Polls are showing that support for same-sex marriage has been growing sufficiently in just a few years. The main poll that shows this is one conducted by Newsweek. Newsweek.com posted an article, detailing the results:

Fifty-five percent of respondents favored legally sanctioned unions or partnerships, while only 39 percent supported marriage rights. Both figures are notably higher than in 2004, when 40 percent backed the former and 33 percent approved of the latter. When it comes to according legal rights in specific areas to gays, the public is even more supportive. Seventy-four percent back inheritance rights for gay domestic partners (compared to 60 percent in 2004), 73 percent approve of extending health insurance and other employee benefits to them (compared to 60 percent in 2004), 67 percent favor granting them Social Security benefits (compared to 55 percent in 2004) and 86 percent support hospital visitation rights (a question that wasn't asked four years ago). In other areas, too, respondents appeared increasingly tolerant. Fifty-three percent favor gay adoption rights (8 points more than in 2004), and 66 percent believe gays should be able to serve openly in the military (6 points more than in 2004).

You have to wonder - if there's so much support for it, why is it only legal in two states?