A plurality of U.S. voters support same-sex marriage, a reversal from four years ago when the public clearly opposed such unions, a poll released today shows. Most voters also support the legalization of marijuana, according to the survey by Hamden, Connecticut-based Quinnipiac University. In the Nov. 6 election, voters in three states approved measures legalizing same-sex marriage and in two states legalized recreational marijuana use. The poll shows 48 percent backing same-sex marriage while 46 percent oppose it. In a 2008 Quinnipiac survey, 55 percent were against same-sex marriage while 36 percent favored it. “It seems pretty clear that attitudes toward same-sex marriage in American society are changing rapidly,” said Peter A. Brown, assistant director of Quinnipiac’s polling institute. “While the country remains split on the issue, supporters have come pretty far in the last four years.” Much of the support comes from voters ages 18 to 29, who back it by almost 30 percentage points -- 63 percent to 35 percent.