G.O.P. Senator Says He Has a Gay Son, and Backs Gay Marriage

Mr. Portman’s revelation makes him the only sitting Republican senator to publicly support giving gay men and lesbians the right to marry, and one of the most prominent so far of a growing number of Republicans to publicly oppose their party on the issue.

In a series of interviews and an op-ed article published in The Columbus Dispatch, Mr. Portman, at times nervously wringing his hands, said that he did not want his son Will, who is 21, treated any differently because of his sexuality.

“I’ve come to the conclusion that for me, personally, I think this is something that we should allow people to do, to get married, and to have the joy and stability of marriage that I’ve had for over 26 years,” he told CNN. “That I want all of my children to have, including our son, who is gay.”

Mr. Portman’s announcement raises more difficult questions for the Republican Party, which is trying to rebuild after the loss of the 2012 presidential election but still holds firmly to positions on issues like gay marriage and immigration that are alienating to many voters.

His position drew a cool response from some quarters and puts him at odds with his party’s leaders in Congress, who have long looked at him as a faithful conservative and loyal ally. A spokesman for Speaker John A. Boehner, who is also from Ohio, said Friday that while Mr. Boehner “respects” Mr. Portman’s position, “the speaker continues to believe that marriage is between a man and a woman.”

A spokesman for Senator Mitch McConnell of Kentucky, the Republican leader, had no immediate comment but said that Mr. Portman did call the senator this week to inform him that he would be making the announcement.

In making the argument for same-sex marriage, Mr. Portman chose not only to articulate his thoughts in personal terms, but did so in a way intended to resonate with conservatives as well.

“We conservatives believe in personal liberty and minimal government interference in people’s lives,” he wrote in the op-ed. “We also consider the family unit to be the fundamental building block of society. We should encourage people to make long-term commitments to each other and build families, so as to foster strong, stable communities and promote personal responsibility.”

Mr. Portman, a former budget director for President George W. Bush, was on the Romney campaign’s short list of possible vice-presidential candidates last year. And he said that he had disclosed his son’s sexuality — which he learned of two years ago — to the campaign.

Beth Myers, the Romney adviser who led the vice-presidential candidate search, said on Friday that the issue had nothing to do with the decision not to select Mr. Portman.

Mr. Portman was a sponsor of the 1996 Defense of Marriage Act that is now being reviewed by the Supreme Court, with arguments scheduled for this month. That case, he said, was a factor in his decision to speak out.

Last month, dozens of prominent Republicans — including top aides to Mr. Bush, four former governors, two members of the House of Representatives and Ms. Myers — signed a legal brief urging the Supreme Court to declare that gay couples have a constitutional right to wed.

As a congressman and later as a senator, Mr. Portman received low ratings from the Human Rights Campaign, a national group promoting gay rights. He received a zero out of 100 as a member the House in the 108th Congress. And in the 112th Congress from 2011 to early 2013, he received a 15 out of 100 after his election to the Senate.

“At the time, my position on marriage for same-sex couples was rooted in my faith tradition that marriage is a sacred bond between a man and a woman,” he wrote in the op-ed. “Knowing that my son is gay prompted me to consider the issue from another perspective.”

Religious conservatives reacted strongly to Mr. Portman on Friday, with some saying that he had turned his back on Christianity. “Senator Portman speaks like so many who call themselves Christians but actually don’t spend much time dwelling on the Word of God,” wrote Erick Erickson, the conservative commentator, on Twitter.

Others were harsher. The Traditional Values Coalition, a religious group that is often vocal on gay issues, issued a statement that equated homosexuality with drunken driving and mocked Mr. Portman, writing, “My child is a drunk driver and I love him.”

Will Portman did not respond to e-mails seeking comment on Friday. But he posted on his Twitter page, “Especially proud of my dad today.”