WASHINGTON (AP) -- 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.
With the issue of immigration also shifting rapidly under Republicans' feet, they seem increasingly focused -- and united -- on one overarching goal: keeping income taxes from rising. Their solidarity on that issue is hindering President Barack Obama's efforts to make higher tax revenue part of a compromise approach to deficit spending and expensive social programs.
These trends raise the possibility that the GOP -- reeling after losing the popular vote in five of the last six presidential elections -- will lessen its identity 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 a lesbian, became arguably the best-known Republican to embrace gay marriage with his announcement 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, who shares Portman's Cincinnati background, 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."
In January, Boehner chastised the Obama administration for dropping its legal defense of the Defense of Marriage Act, which the Supreme Court is to consider this month. Boehner authorized the continued use of public funds to defend the law in courts.
Boehner's latest comments reflect the change among many mainstream Republicans, who now deal with gay marriage in largely unemotional, legalistic terms rather than emotional terms about sin and God's will.
Congress now has several openly gay members, including a senator, Wisconsin Democrat Tammy Baldwin.
At the U.S. House, which was in session Friday, several conservatives had little or nothing to say about Portman's announcement.
Gay marriage "is not the most front-burner issue," said Rep. James Lankford, R-Okla. "We still have the same legal issues we've always had with the Defense of Marriage Act," which he supports, he said.
Citing Obama's position, he said, "It's more a separation of powers issue than it is anything else." Lankford said other Republicans have supported same-sex marriage, so "this is not anything new."
In another legal matter -- California's ban on same-sex marriage -- all 21 state attorneys general who have signed legal briefs or letters urging the Supreme Court to uphold the law are Republican.
White House spokesman Josh Earnest said Friday: "What is clear is that we are witnessing a pretty significant sociological shift in this country."
"It's happening right before our eyes in a way that says a lot about our country, that we have a country where we prioritize equality and fairness," he said.