Newly declared Republican presidential candidate Marco Rubio said Sunday that he believes being gay is not a choice.

“I … don’t believe that your sexual preferences are a choice for the vast and enormous majority of people. And, In fact, the bottom line is that I believe that sexual preference is something people are born with,” Rubio, a senator from Florida, told “Face the Nation” host Bob Schieffer.

Although Rubio continues to be generally opposed to gay marriage, it appears his position on the key social issue is evolving. Just Tuesday, Rubio told reporters that he has never supported a national constitutional amendment banning gay marriage, despite a 2010 voter guide from a leading social conservative group indicating he supported such an amendment.

RELATED: Scott Walker has attended gay wedding reception

“It’s not that I’m against gay marriage,” Rubio said in the interview Sunday. “I believe the definition of the institution of marriage should be between one man and one woman.” Rubio also re-iterated that he believes the legality of gay marriage should be decided at the state level, “and if a state wants to have a different definition, you should petition the state legislature and have a political debate.”

“I don’t think courts should be making that decision, and I don’t believe same sex marriage is a constitutional right,” Rubio added.

Rubio wasn’t the only 2016 hopeful to weigh in on gay marriage Sunday. Wisconsin Gov. Scott Walker, a potential 2016 GOP contender, told msnbc that he has attended a reception for a gay wedding in the past. Still, Walker said he believes marriage should be between a man and a woman, and that he “support[s] the constitution of the state.”

Hillary Clinton, on the other hand, has taken a firm stance in support of marriage equality. On her second day on the campaign trail, a spokesperson issued a statement saying that Clinton hopes the Supreme Court will guarantee same-sex couples the “constitutional right” of marriage.

