I think I heard a poll that 61% of Republicans (or maybe young Republicans) accept gay marriage. This is a sea change since 2008, in fact, right up to the 2012 election Obama claimed that a real marriage couldn't be anything other than one man and one woman. Government officials and judges have changed the law, but the people haven't voted. It really started in the 1970s with the feminist movement. What better way to say men don't matter? Children are for aborting if it's not convenient. The terrible AIDS plague helped it along by creating a huge block of sympathy because it affected primarily gays, regardless of the misinformation we were given. But mainly, the population just stopped caring about marriage.
I remember watching Phil Donahue when he was still a local show in the early 1970s from Dayton interviewing couples who claimed marriage just wasn't important. It's like a couple of generations handed homosexuals their tattered hand-me-downs they didn't want any more.