WASHINGTON — A Republican senator's embrace of gay marriage is the latest sign of soul-searching in a party struggling to adapt in a society whose demographics — and views on emotional issues — are changing fast.
Gay marriage still divides the party, with the conservative wing strongly opposed. But an increasing number of Republicans, now including Sen. Rob Portman of Ohio, are reversing course. Many others simply downplay the subject.
These trends raise the possibility that the GOP — reeling after losing the popular vote in five of the last six presidential elections — will identify less with hot-button social issues and sharpen its emphasis on tax and spending matters.
Portman announced Friday that he now supports gay marriage, linking his stand to learning that one of his sons is gay.
A former U.S. trade representative and White House budget chief, Portman is seen as one of the party's most knowledgeable and effective leaders. Mitt Romney considered him to be his running mate last year. Portman says he told Romney of his son Will's sexuality but does not believe it affected Romney's decision.
As a U.S. House member in 1996, Portman supported the Defense of Marriage Act, or DOMA. It defines marriage as between a man and a woman and bars federal recognition of same-sex marriage.
Portman's reversal makes him the only Senate Republican to openly back gay marriage.
"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," Portman wrote in an op-ed article in The Columbus Dispatch.
He said he had talked to his pastor and others, including Senate Minority Leader Mitch McConnell, R-Ky., who opposes gay marriage, and to former Vice President Dick Cheney, who supports it.
Cheney, whose younger daughter is lesbian, became arguably the best-known Republican to publicly embrace gay marriage in June 2009.
Portman said his previous views on marriage were rooted in his Methodist faith. However, he wrote, "Ultimately, for me, it came down to the Bible's overarching themes of love and compassion and my belief that we are all children of God."
Despite his party's struggles with Americans' increasing acceptance of gay rights, many GOP leaders met Portman's news with silence or a shrug.
A spokesman for House Speaker John Boehner, R-Ohio, said the senator "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."
The leader of a conservative group that promoted passage of a 2004 amendment in Ohio to ban gay marriage said he has heard from several people upset by Portman's stance.
"They feel betrayed," said Phil Burress, president of Citizens for Community Values. "They're not mad. They're sad and betrayed."
Ohio Republican Party Chairman Bob Bennett agreed that some Republicans are unhappy, but he said he received more phone calls Friday about the governor's budget. He said Portman has "taken a great deal of time to think it through and I certainly respect his right to make up his own mind."
Richard Socarides, who was President Bill Clinton's top adviser on gay issues, said Portman's son Will "proved once again that the most powerful political act any gay person can take is coming out." He said polls show that "people who know a gay person are far less likely to support discrimination."