(Cincinnati)— Republican U.S. Sen. Rob Portman of Ohio says he now supports gay marriage because one of his sons is gay.

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.

Portman says he reconsidered gay marriage from a different perspective, that of a father who wants all three of his children to have happy lives with people they love.

He says he discussed the issue with his pastor and others, including former Vice President Dick Cheney, whose daughter is a lesbian.

As a member of the House in 1996, Portman had voted for the Defense of Marriage Act, which defines marriage as between a man and a woman and bars federal recognition of same-sex marriage.

"This is a principle position that he has held for all these years and to change a principle position based on a family situation that appeared to be very private was quite a shock," said Phil Burris, president of Citizens for Community Values, the group that helped pass a 2004 ban on gay marriage in Ohio.

Burris called the situation "tragic" and said during a phone call with the Senator Thursday he told Portman he would pray for the family. He added that Portman assured him he would not be campaigning for the issue and was still against the U.S. Supreme Court overturning DOMA.

"He said that if the states wanted to legalize same-sex marriage they should have a right to but also if they wanted to prohibit it they should have a right to, so he saw it as a states' rights issue."

Burris wishes Portman had kept the issue a private matter. He thinks Portman's son forced him into going public. Burris also says this could really hurt Portman politically.

"This could spell trouble for Rob down the road. As far as going out and seeking someone to run against him, we're not even considering that right now although he certainly has opened the door for that," Burris said.

Portman won't be getting his group's endorsement because he has an opposite view on an issue Burris calls "non-negotiable."

"Marriage equality is coming," said Ian James, co-founder of Freedom Ohio, a group pushing to overturn the 2004 ban on gay marriage in Ohio. "It's going to happen and it's going to happen in Ohio sooner rather than later. It's not a matter of if it's a matter of when."

The group says they have the signatures needed to put the issue before voters as early as November, but they are waiting for the right time. That decision will be made before July.

James calls Portman's decision a "game changer" and shows Republicans that it is okay to come out and support same-sex marriage.

"The times have changed. This is not 2004 any more. Ohioans get it. They support the freedom to marry."

Burris disagrees saying that people have their minds made up on the issue and he hasn't seen anything that leads him to believe that they've changed.

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(Copyright © 2013 by the Associated Pressa and Clear Channel, all rights reserved. Photo by Drew Angerer/Getty Images)