FILE - In this Aug. 29, 2012 file photo, Ohio Senator Rob Portman waves to the delegates during the Republican National Convention in Tampa, Fla. Portman said Thursday, March 14, 2013 that he now supports gay marriage and says his reversal on the issue began when he learned one of his sons is gay. (AP Photo/J. Scott Applewhite, File)
FILE - In this Aug. 29, 2012 file photo, Ohio Senator Rob Portman waves to the delegates during the Republican National Convention in Tampa, Fla. Portman said Thursday, March 14, 2013 that he now supports gay marriage and says his reversal on the issue began when he learned one of his sons is gay. (AP Photo/J. Scott Applewhite, File)

By ANN SANNER

Associated Press

COLUMBUS, Ohio (AP) - The chairman of the Ohio Republican Party said Friday the state GOP will continue to stand behind U.S. Sen. Rob Portman, who has announced he now supports gay marriage.

Chairman Bob Bennett acknowledged some Republicans will disagree with Portman's decision, but Bennett said he respects the junior senator's right to make up his own mind.

"Certainly, you can't question Rob's conservative credentials when it comes to issues affecting the Republican Party," Bennett said in an interview. "I think we'll be fine. And the party is a big tent. We welcome people holding a wide range of positions on some very difficult issues."

Still, Bennett said the state GOP received a flurry of phone calls for about two hours on Friday morning from people upset about Portman's stance. But he said the calls were fewer in number than those offering their opinions on Republican Gov. John Kasich's state budget proposal.

The calls about Portman had died down by the afternoon. "So I'm not sure how big of an issue it is among the Republican family right now," he said.

Portman told reporters Thursday in Washington that his views began changing in 2011 when his college-age son, Will, told his parents he was gay. In an op-ed published Friday in The Columbus Dispatch, he said the decision came after much thought.

"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," he wrote.

As a member of the House in 1996, Portman voted in favor of the Defense of Marriage Act, which 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 back gay marriage.

Asked whether Portman's decision would change the level of financial support or help from the state GOP party, Bennett said, "Absolutely not."

Portman does not face re-election until 2016. He won his seat in 2010 with almost 57 percent of the vote.

A group working to overturn Ohio's ban on same-sex marriage praised Portman's comments, as did Ohio's senior senator, Democrat Sherrod Brown.

"I look forward to working with him to ensure that all Americans have the ability to marry, regardless of whom they love or where they live," Brown said in a written statement.

Brown voted against DOMA while he was a member of the U.S. House.

Portman told reporters Thursday he would back overturning Ohio's state ban on same-sex marriage if it comes up in a voter referendum.

"I'm going to be supportive of Ohioans having the opportunity to marry," he said. "I would not plan to take a leadership role in this, but people will know my position."

The leader of a conservative group that promoted passage of the state's 2004 amendment to ban gay marriage said the stance will affect Portman's political future.

"I can almost assure you, based on what I'm hearing right now, that he's going to have competition in the primary," said Phil Burress, president of Citizens for Community Values.

Burress' group, based in the northern Cincinnati suburb of Sharonville, helped rally a strong turnout among Christian evangelical voters for the amendment to the Ohio Constitution defining marriage as between a man and a woman. The turnout added crucial votes for President George W. Bush's narrow victory in Ohio that clinched his re-election.

Burress has known Portman for more than 20 years, and said the senator informed him Thursday night about his decision. He said he feels Portman let a family situation affect the way he conducts his politics.

"If you're going to be a Republican, you can't be wrong on our core issues," he said.

Reaction from the governor's office and other leading Ohio Republicans was more toned down.

Kasich spokesman Rob Nichols said in an email: "That's not the governor's position but he respects the Senator's decision and wishes him and his family well."

Doug Preisse, a county GOP chairman in central Ohio who's openly gay, said he expects Portman's stance will spark debate on the topic within the party.

"There's certainly going to be Republicans who are going to hail this as progress and there will be others who criticize it - but within the party there's room for that," said Preisse, who heads the Franklin County Republican Party.

"I would say, too, that the reaction to this announcement is different today than it would have been 20 years ago," Preisse added. "And it's probably going to be different in 20 years than it is today."