WASHINGTON - Ohio Sen. Rob Portman is now the only Senate Republican to support gay marriage, and he says he changed his mind on the issue after his college-age son told his parents two years ago that he's gay.

Writing Friday in The Columbus Dispatch, Portman says if two people are ready to make a "lifetime commitment to love and care for each other in good times and in bad," the government shouldn't keep them from getting married.

He says his son Will told Portman and his wife that being gay wasn't a choice, but was "part of who he was." The senator says he and his wife were very surprised, but also supportive.

He told reporters Friday that his earlier views on marriage were rooted in his Methodist faith.

Portman was considered but not chosen as Mitt Romney's running mate last year.

Portman voted for the Defense of Marriage Act when he was in the House in 1996, but now says he'd like for Congress to repeal the part of that law that bans federal recognition of gay marriage. He still says states shouldn't be forced to recognize those marriages.