Exit polls and other surveys from the November election suggest that resistance to same-sex marriage is shrinking and mainly concentrated among certain segments of the population: older people, white evangelical Christians and non-college-educated whites.

That is the analysis of a new study of the data by two pollsters, one a Democrat and the other a Republican.

“Significant opposition to the freedom to marry is increasingly isolated within narrow demographic groups while a much broader and more diverse majority are ready to let same-sex couples marry,” wrote Joel Benenson, who led President Obama’s polling operation in 2008 and 2012, and Jan van Lohuizen, who did the same job for former President George W. Bush.

Their research, being released Thursday, was commissioned by Freedom to Marry, an organization that promotes establishing a national right to same-sex marriage. It is a follow-up to a May 2011 report in which the pollsters found support for such unions had accelerated, starting around 2009.

That appeared to be borne out by the 2012 election results. Until last year, voters had rejected same-sex marriage every time it had been put to the test in statewide elections. But in 2012, the four states — Maine, Maryland, Minnesota and Washington — with ballot questions on the issue either voted in favor of allowing such unions or rejected a ban on them.

Benenson noted that the question was not asked on exit polls in 2004 and 2008.

Overall, the 2012 exit polls, which were conducted in 31 states, showed 49 percent supporting same-sex marriage in their states and 46 percent opposing it.

The pollsters found that opposition centered primarily in a few demographic groups.

Voters age 65 and older expressed opposition to allowing such unions in their states, by a 21 point margin, with 37 percent supporting them and 58 percent opposing. Those younger than 65 favored them by 8 points, 52 percent to 44 percent.

The disparity was even greater among religious groups, broken down along racial lines. White evangelical Christians opposed same-sex marriage by nearly 3 to 1. But every nonevangelical group expressed support for such unions by double-digit margins.

Meanwhile, African-American voters who described themselves as evangelical or born again were narrowly divided, with 47 percent saying it should not recognize same-sex marriage and 45 percent saying it should.

Another “pocket of opposition,” the pollsters said, is white voters who do not have a college degree.

Only 40 percent supported same-sex marriage, compared with 56 percent who oppose it.

Other groups supported such unions by 54 to 38 percent among nonwhite, non-college graduates; 56 to 41 percent among white college graduates, and 58 to 35 percent among nonwhite college graduates.