Interesting for many reasons. Timing: He’s dropping this during CPAC, when political media is focused on competing factions within conservative thought, and shortly before the Supreme Court takes up a landmark case on Prop 8 and DOMA. Enthusiasm: He didn’t casually mention this during a standard Q&A with a reporter. He called three Ohio journalists to his office for the announcement, granted CNN an on-camera interview, and published an op-ed in today’s Columbus Dispatch. He’s really throwing some weight behind it. Prominence: Portman was, of course, a shortlister for VP and is the lone GOP senator from America’s ultimate swing state. More than that, he’s the first sitting Republican member of the Senate to endorse legalizing same-sex marriage. The Supreme Court amicus brief filed by pro-gay-marriage Republicans a few weeks ago was conspicuous for its lack of any big-name incumbents as signatories. Portman’s a big name.

Why’d he switch? Like Dick Cheney, whom Portman met with to discuss this, his view changed when he found out someone in his family is gay:

Portman said his own evolution on the issue began in 2011, when [his son] Will, then a freshman at Yale University, made a stunning revelation.

“Will … came to Jane and me and announced that he was gay, that it was not a choice. It was who he is and he had been that way since he could remember,” Portman recalled of the conversation. “Jane and I were both surprised, very surprised, but also very supportive of him. Our reaction was not about policy or positions. It was about him as a son and letting him know we were 110 percent supportive of him.”

His son’s homosexuality “allowed me to think about this issue from a new perspective, and that’s as a dad who loves his son a lot,” Portman said. He said he wants Will to have the same chance at an enduring relationship, “like Jane and I have had for over 26 years.”…

Portman said his previous views on marriage were rooted in his faith.

But “the overriding message of love and compassion that I take from the Bible . . . and the fact that I believe we are all created by our maker . . . that has all influenced me in terms of my change on this issue,” he said.

He says he told the Romney camp about his son last year when he was vetted for VP and that they told him it was no problem. Imagine, though, putting Portman on the ticket and then having news break that the vice presidential nominee, who once voted for a constitutional amendment to ban gay marriage, has a gay son. The media’s coverage of Portman for the rest of the campaign would have been filtered through the issue of SSM and Romney surely knew it. Is that something he would have wanted given his intense messaging emphasis on the economy?

Mollie Hemingway makes a fair point, too:

Leaving apart the question of whether marriage law should be changed, this strikes me as a problematic approach. I mean, marriage law should be changed or it shouldn’t be changed — but it shouldn’t hinge on the sexual attractions of one senator’s son, should it?

What if a conservative senator said, “I’m reversing my views on whether abortion should be legal because my daughter got pregnant and wished she weren’t.”

One of the fascinating things about society today is that personal experience trumps everything else in argumentation. Very few people seem to care about fundamental truths and principles while everyone seems to care about personal experience and emotion. It’s the Oprahfication of political philosophy.

Yeah, I’m loath to scold the guy for his reasoning given that I agree with him and that he’s taking on a bit of political risk in doing this, but why did he need his son to come out to get him to look at this issue from the perspective of someone who’s gay? He’s been a professional legislator for years; he’s supposed to consider all sides of an issue when deciding which policy to support. That’s a surprisingly parochial approach to a national debate that’s been rolling around for a solid decade now. Makes me wonder if his feelings on the subject really did change recently or if he’s always quietly been open to gay marriage but only felt politically safe to announce it once he discovered his son’s orientation. Conservative primary voters may be less likely to hold it against him if they think it’s a decision driven by fatherly love for his son.

Anyway, who’s next? The real significance of Portman endorsing SSM is that it gives political cover to other GOP incumbents who might secretly agree with him to speak up too. Republicans from solidly red states will remain opposed but there are plenty of purple-state possibilities. Susan Collins seems like a given. Murkowski can probably get away with it in Alaska. Mark Kirk would pay no heavy penalty in Illinois. Maybe Kelly Ayotte too, or do her national ambitions prevent that (for now)? There’ll be more.