South Carolina Sen. Lindsey Graham, who is expected to announce a presidential bid, says if the Supreme Court rules same-sex marriage bans unconstitutional, then it will be time for Republicans to move on.

Graham told Boston Herald radio on Monday that society is changing and a constitutional amendment defining marriage as between a man and woman is no longer possible.

"Well, can you be for traditional marriage? Yes. Am I for traditional marriage? Yes, I believe marriage has stood the test of time between a man and a woman, ordained by God, and that's -- most societies have been organized around that concept," Graham said.

"Things are changing, so at the end of the day, being for traditional marriage without animosity is where I stand. If the Supreme Court rules sometime this year that same-sex marriage bans are unconstitutional, then that will be a defining moment in that debate. It will be time for us to move forward as a society."

Graham added he didn't see how a constitutional amendment defining marriage as between a man and a woman was possible.

"I just don't see how you get a constitutional amendment defining marriage as between a man and a woman ratified by 3/4 of the states given the way the lay of the land is today. So the courts gonna hear the case," he said. "People who are social conservative, hold your head up high. Be proud of speaking for the unborn, I'm a pro-life guy with exceptions of rape and incest. When a woman is raped, it is not the will of God, it is a crime, and the perpetrator should be punished accordingly. The woman will make that decision about what to do after being the victim of a crime."

Graham concluded that at the end of the today the changing "social structure" is a normal part of democracy.

"But at the end of the day, this whole social structure that's changing is part of democracy, is part of society," Graham said.