Speaking at the Conservative Political Action Conference on Thursday, Sen. Marco Rubio asserted the right of states to define marriage — marking a major shift in the gay marriage debate.

Back in 2004, when President Bush proposed an amendment to the U.S. Constitution defining marriage as being between a man and a woman at the federal level, that was the default position for elected conservatives. Those Republicans who argued in favor of leaving the decision up to the states were seen as moderates or more libertarian-minded.

But the debate has shifted dramatically in the intervening years. That’s why it was eye-opening to hear Rubio, a major conservative in the Senate speaking at the largest annual gathering of conservatives, declare: “Just because I believe that states should have the right to define marriage in a traditional way does not make me a bigot.”

The line was met with applause from the CPAC audience.

Just a few years ago, that sentence might have read, “Just because I believe that states shouldn’t be allowed to redefine marriage does not make me a bigot.”

It’s telling how far the gay marriage debate has moved in the direction of its proponents in such a short period of time.