Ohio Republican Sen. Rob Portman's endorsement of same-sex marriage rights on Friday is the latest high-profile example of a sea change within the conservative movement toward gay rights.
A trickle of GOP leaders have begun to back the rights of gay and lesbian couples to marry, and activists at the conservative movement's signature gathering this week express tolerance for Republicans who support same-sex marriage, even if they personally disagree.
Portman, an influential senator whom Mitt Romney almost selected last year as his running mate, announced that he had changed his position toward same-sex marriage because one of his sons is gay.
"I have come to believe that if two people are prepared to make a lifetime commitment to love and care for each other in good times and in bad, the government shouldn't deny them the opportunity to get married," the Ohio senator wrote in an op-ed for the Columbus Dispatch.
He's not the only high-profile Republican to back marriage rights for same-sex couples, either.
Jon Huntsman, a GOP presidential candidate in 2012 who had endorsed civil unions, said this year that he supports marriage rights. Furthermore, he framed it in conservative terms.
Related: Portman announces his support for same-sex marriage
"There is nothing conservative about denying other Americans the ability to forge that same relationship with the person they love," he wrote.
And Theodore Olson, a former solicitor general for President George W. Bush, has been one of the lead attorneys challenging California's Proposition 8, a ballot initiative barring same-sex marriage in that state. (Portman fretted in his op-ed that a court decision might hamper the political movement toward legalizing gay and lesbian weddings.)
And Fred Malek, a Republican power-broker, told NBC News this week that conservatives shouldn't feel threatened by gays and lesbian couples who wish to marry.
"I've always felt that marriage is between a man and a woman, but other people don't agree with that," he said. "People should be able to live their lives the way they choose. And it's not going to threaten our overall value system or our country to allow gays to marry, if that's what they want to do."
In response to the Portman endorsement, a spokesman for Republican House Speaker John Boehner said, "Senator Portman is a great friend and ally, and the Speaker respects his position, but the speaker continues to believe that marriage is between a man and a woman."
It was a sentiment echoed by House Majority Leader Eric Cantor, who said, "As a matter of personal religious conviction, I've always believed in marriage, I believe in the traditional marriage between a man and a woman. But again, I think Senator Portman is entitled to his positions, and you know we are a party of diversity and, I think, of respect."
Gay rights is an issue that has changed rapidly in just a few years. President George W. Bush endorsed a constitutional amendment to ban gay marriage, and President Barack Obama had said he did not support same-sex marriage when he was first running for office in 2008.
But Obama completed his "evolution" on gay rights (hastened by Vice President Joe Biden's inadvertent pronouncement of support for same-sex marriage) and announced his support for marriage rights last year. Romney had re-iterated his opposition to gay marriage at the time, but declined to use it as a cudgel versus Obama, calling same-sex marriage a "tender" issue.
There's still resistance, though, to the issue. Florida Sen. Marco Rubio, R, received a loud cheer on Thursday at this week's Conservative Political Action Conference when he said: "Just because I believe that states should have the right to define marriage in a traditional way does not make me a bigot."
Nonetheless, the broader change reflects broader public opinion. A plurality of Americans — 47 percent — said they support same-sex marriage, according to a Quinnipiac University poll released earlier this month. Forty-three percent of Americans oppose same-sex marriage. Looking inside of those numbers, independents back marriage rights by a 12-point margin, and nearly a quarter of Republicans — 23 percent — said they support same-sex marriage.
But while the GOP has been slower to embrace same-sex marriage, the party's internal struggle toward same-sex marriage was on display this week at CPAC.
While a gay Republican group, GOProud, was formally barred from sponsoring CPAC this year, an informal discussion organized by conservatives who support same-sex marriage was one of the most popular on the confab's first day.
The split is undeniably generational, too; young conservatives here at CPAC are much more inclined to support same-sex marriage, even if they don't personally support it.
"I would say that the majority of my friends — it's not so much that we agree with it, it's just that we don't care," said Gabe Snyder, a 20-year-old college student from North Carolina in attendance at CPAC. He said he personally opposes same-sex marriage, but believed that a generational change was afoot.
"I think this generation coming up is going to be different from our parents," said Snyder.
And Renee Knight Leberry, from South Carolina, who also personally opposes same-sex marriage, said that she didn't think Portman's conservative credentials were diminished at all by his pronouncement on Friday.
"I respect him; it's his choice, and as a Christian conservative, I respect anybody's choice. That's his son, and he loves his son. I don't think it would be right to judge him for supporting his son."