Ohio Senator Rob Portman, the first sitting GOP senator to endorse gay marriage, says he has been asked a lot about his shift on the issue by constituents back home.

“People have been very respectful and I've had a lot of good conversations about it,” Portman told Columbus CBS affiliate WBNS-TV.

“I don't think churches should be required to perform weddings they don't approve of, or recognize marriages they don't approve of, and that's something I've talked to a lot of Ohioans about this past week that I've been home. This is not about telling churches what they have to do. It's about letting individuals make that choice for themselves.”

Portman said that he had dropped his opposition to marriage equality after his son, Will Portman, told him and his wife Jane that he's gay.

“I had a change of heart based on a personal situation, but the more I think about it and the more I was able to delve into the issue, the more I believe that this is something that would be better, actually, for stability and the kinds of benefits you get from marriage.”

“I suspect that people who have colleagues or friends or family who are gay who talk to them, in my case, my son did talk to me about my positions on the issues, and that can be very influential,” Portman said.

Citizens for Community Values, the group which led the 2004 campaign to approve Ohio's constitutional amendment that prevents the state from recognizing any relationship other than a heterosexual marriage, is spearheading an effort to oust Portman based on the issue in 2016.

(Related: Gay marriage foes organize to oust Rob Portman.)