The rise in support for same-sex marriage over the past decade is among the largest changes in opinion on any policy issue over this time period. A new national survey finds that much of the shift is attributable to the arrival of a large cohort of young adults – the Millennial generation – who are far more open to gay rights than previous generations. Equally important, however, is that 14% of all Americans – and 28% of gay marriage supporters – say they have changed their minds on this issue in favor of gay marriage.