According to the New York Times, the shift on same-sex marriage has captured the headlines, but the changes on views toward marriage are much broader than one issue.
The latest Gallup social issues survey shows changing social views since 2001. They show that not just support for same-sex marriage is changing.
Approval of unwed parenthood (45 percent in 2001, 61 percent now), divorce (59 percent then, 71 percent today), and premarital sex (53 percent then, 68 percent now) are on the rise.
Also, the acceptance of polygamy has more than doubled. Support for “plural matrimony” rose from 7 percent to 16 percent during the same period.
http://www.nytimes.com/2015/05/31/opinion/sunday/ross-douthat-the-prospects-for-polygamy.html?_r=0