In his 2012 history book, GOP presidential candidate Ben Carson wrote that same-sex marriage contributed to the decline of the Roman Empire.

"As a Bible-believing Christian, you might imagine that I would not be a proponent of gay marriage," Carson wrote in his book, America the Beautiful. "I believe God loves homosexuals as much as he loves everyone, but if we can redefine marriage as between two men or two women or any other way based on social pressures as opposed to between a man and a woman, we will continue to redefine it in any way that we wish, which is a slippery slope with a disastrous ending, as witnessed in the dramatic fall of the Roman Empire."

"I don't believe this to be a political view, but rather a logical and reasoned view with long-term benefits to family structure and the propagation of humankind," Carson wrote. "When children grow up in an environment with loving parents who provide security, they are free to be happy and playful and eager to learn. God obviously knew what he was doing when he ordained the traditional family, and we should not denigrate it in order to uplift some alternative."

Ben Carson has in the past blamed "political correctness" for the fall of the Roman Empire.

Similarly, in a 1997 speech to the National Prayer Breakfast, Carson blamed sports and entertainment for the empire's decline.

"We have to change the tremendous emphasis on sports and entertainment and lifestyles of the rich and famous," Carson said. "Because, see, there were other great nations that went that pathway: Egypt, Greece, Rome, they were all at the pinnacle, just like the the USA, and then they forgot about the things that made them great and became enamored with things that weren't so important. And where are they today? And some people think that that can't happen here, but it can. And we have a real obligation to do something to do something change that."