In April, 2009, when we last took a survey of gay marriage polls, we found that support for it had converged somewhere into the area of 41 or 42 percent of the country. Now, it appears to have risen by several points, and as I reported yesterday, it has become increasingly unclear whether opposition to gay marriage still outweighs support for it.

Here is a version of the graph we produced in 2009, but updated to include the dozen or so polls that have been conducted on it since that time, as listed by pollingreport.com. I have also included opinions on gay marriage from the General Social Survey, which asked about gay marriage as long ago as 1988.

The LOESS regression line now shows 50 percent opposed to gay marriage and 49 percent in support — basically too close to call.

One caveat is that LOESS regression tends to be fairly sensitive on the endpoints, and so yesterday’s CNN survey, which showed the pro-gay marriage position leading 50.5-48.5, makes a fair amount of difference. But even if we ignored that survey, support for gay marriage would instead be in the range of 45-46 percent (and opposition between 51-52 percent): that would reflect acceleration in the rate of support for gay marriage, about a 4-point gain over the past 16 months, faster than the long-term rate of increase, which has been between 1 and 1.5 points per year.

Something to bear in mind is that it’s only been fairly recently that gay rights groups — and other liberals and libertarians — shifted toward a strategy of explicitly calling for full equity in marriage rights, rather than finding civil unions to be an acceptable compromise. While there is not necessarily zero risk of backlash resulting from things like court decisions — support for gay marriage slid backward by a couple of points, albeit temporarily, after a Massachusetts’ court’s ruling in 2003 that same-sex marriage was required by that state’s constitution — it seems that, in general, “having the debate” is helpful to the gay marriage cause, probably because the secular justifications against it are generally quite weak.