The History of Same Sex Marriage Support

I've read various predictions that the majority of Americans will finally approve of same sex marrige sometime before 2020, with the year varying depending on who was making the prediction.  To my surprise and delight, I found that the crossover has apparently already happened.  The majority of Americans today now support same sex marriage.   The following chart on the legality of same sex marriage is from the 2010 edition of the General Social Survey.  Andrew Sullivan calls it "one of the most successful political, social and cultural movements in history".