Polling on Gay Marriage

Nate Silver has done a sophisticated analysis of polling trends on gay marriage, "Fact and Fiction on Gay Marriage Polling." He concludes that:

Support for gay marriage ... is strongly generational ... Civil unions have already achieved the support of an outright majority of Americans, and as those older voters are replaced by younger ones, the smart money is that gay marriage will reach majority status too at some point in the 2010's.

Not so fast, actually.

Note this methodological note from Silver's plotted-data of PollingReport surveys:

This chart includes all surveys in the PollingReport.com database, except those where the respondent was given a three-pronged choice between gay marriage, civil unions and nothing.

This is problematic. Recent surveys, from Iowa Iowa and nationally, have queried support for gay marriage outside of this binary formulation (gay marriage/civil unions). Here's Newsweek's key question item, with only 31 percent favor full same-sex marriage rights:

Thinking again about legal rights for gay and lesbian couples, which of the following comes CLOSEST to your position on this issue? Do you support FULL marriage rights for same-sex couples, OR support civil unions or partnerships for same-sex couples, BUT NOT full marriage rights, OR do you oppose ANY legal recognition for same-sex couples?

Now, while there is evidence for the notion that the liberal youth cohort will replace older voters less tolerant of gay marriage (see, for example, "Explaining the Growing Support for Gay and Lesbian Equality Since 1990"), the nature of question wording, as well as the environmental political influences (gay rights protest extremism, activist political mobilization strategies, and so forth), will determine the levels of support for same-sex marriage in the years ahead. With these facts in mind, it seems a bit premature to suggest, as does Silver, "that gay marriage will reach majority status" in just a few years.