Greg Lewis has been studying public opinion on gay rights for about two decades now. And when it comes to attitudes toward same-sex marriage, he’s never seen anything like the past few years.

“In 2008, I published an article saying we haven’t seen any movement on same sex marriage ever,” Lewis, a professor of public management and policy at Georgia State University, admits with a laugh. “But that was using data a few years old. If you look back at the numbers now, you can see that support really began to take off in 2004.” He estimates that by the end of 2011, support was at about 46 percent — up from 30 percent in 2004.

(Greg Lewis)

Lewis’s estimates, which aggregate many different polls over many years to come up with a fuller picture of public opinion on this issue, show that support for same-sex marriage has increased by 16 points since 2004. The increase has been fastest among Democrats and slowest among Republicans. That means the issue has gotten more polarized, too.

Support varies dramatically between different states, Lewis continues. “My most recent estimates suggest majority support for same-sex marriage in 16 states.” With the exception of Alaska, those 16 states are all safe states for Obama. But Lewis’s latest numbers only go through 2011. “If we figure support has gone up another two points in the last year, that would push Wisconsin, Arizona and Maryland into majority-support territory, and Illinois and Minnesota right on the borderline.”

You can argue that these polls overstate the support gay marriage actually has among voters. After all, it’s a perennial loser at the ballot box. But Lewis notes that the same analysis “showed 35 percent support in North Carolina. And that’s pretty consistent with the vote there.”

For all that, Lewis is skeptical that the issue will make much of a difference in 2012. “My guess would be the people who are most intensely motivated by this issue are trapped in their choices. I don’t think that there are many people who are so opposed to same-sex marriage that they’ll vote on that basis and are not already voting for the Republican. And likewise, same-sex supporters for whom this is a voting issue are voting for Obama.”