Sen. Rob Portman (R-Ohio) says he has decided to support gay marriage, two years after his son came out to him as gay.

"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," the Republican, who was on the short list to become former Massachusetts governor Mitt Romney's running mate in the 2012 presidential campaign, wrote in an op-ed that appeared in the Columbus Dispatch on Friday.

"That isn’t how I’ve always felt. As a congressman, and more recently as a senator, I opposed marriage for same-sex couples. Then something happened that led me to think through my position in a much deeper way."