Matthew Cavanaugh/Getty Images

It's no secret that there's a sharp generational divide on same-sex marriage. And in the latest finding to underscore that point, a new Pew survey shows that just over six in ten Republicans between the ages of 18 and 29 support same-sex marriage. Meanwhile, only 22 percent of Republicans over the age of 65 feel the same way.

The huge gap between young and old GOPers helps explain all the tension between the party's desire to evolve and its reluctance to shrug off an older, conservative base. Fifty-four percent of all Americans support same-sex marriage, per Pew, a number that's rapidly rising and, as it does so, puts the GOP more and more at odds with prevailing public opinion.