Andrew Sullivan explains:
Democrats’ and independents’ support for legalized same-sex marriage increased this year by 13 and 10 points, respectively. Republicans’ views on the issue did not change from last year. Clear majorities of both Democrats and independents now support gay marriage, 69% and 59% respectively, contrasted with 28% support among Republicans.
To go from 41 points behind to 8 points ahead in a decade and a half must count as one of the most successful political and social campaigns in history.
Update: more details on this here.