We turn now to a very sudden and personal shift in a person divisive issue in america, gay marriage. A high profile republican who was the kind of wizard of oz behind mitt romney's debates, making... See More
We turn now to a very sudden and personal shift in a person divisive issue in america, gay marriage. A high profile republican who was the kind of wizard of oz behind mitt romney's debates, making headlines of his own tonight, now saying gays should be allowed to marry. That senator is rob portman. The reason behind the change -- his son, behind him in the blue checkered shirt. Abc's chief white house correspondent jonathan karl tonight. Reporter: He's an all-american father fully devoted to his kids. When his middle child, son will, went to college, he revealed to his parents that he had a secret. My son came to , my wife and told us that he was gay, and that it was not a choice, and that, you know, he -- that's just part of who he is and he's been that way ever since he could remember. Reporter: What was your reaction when he told you? Love, support, you know, 110%. Reporter: Surprised? Yeah. Reporter: It's a story many families can relate to. Like when this airman videotaped his own call coming out to his father. Dad, I'm gay. Yikes. Do you still love me? I still love you, son. Reporter: The video went viral. More than 6 million youtube views and counting. And in pop culture, we've watched on "modern family" as jay comes to terms with his gay son, mitch. You played good. I'm proud of you. Really? We should do this again some time. Reporter: But in this case, the dad is rob portman. A powerful and conservative republican senator. He's voted to ban adoption by same sex partners and for a constitutional amendment prohibiting gay marriage. Portman told cnn that his family experience has prompted him to change his views. I think this is something that we should allow people to do. To get married and to have the stability of marriage that I've worked for over 26 years. I want all three of my kids to have it concluding our son who's gay. Reporter: Public opinion has changed dramatically on this, with a majority of americans now favoring gay marriage. But the political views -- the political system has changed much slower. Consider this, david. Now 31 states still have constitutional amendments explicitly banning same sex marriage. Very personal move nor senator portman. Jon karl, thank you. Overseas tonight, and to the
This transcript has been automatically generated and may not be 100% accurate.