Massachusetts Senator John Kerry argues that President Barack Obama has a right to change his mind on gay marriage.

The 67-year-old Democrat made his comments in an op-ed published Sunday in the Boston Globe.

Obama, who supports recognizing gay and lesbian couples with civil unions, has said he's “evolving” on marriage, prompting progressives to call on Obama to “evolve already” and analysts to question whether the move would hurt the president's political future.

Kerry called the debate “phony.”

“Everyone is entitled to his own view, in his own time, including the president,” Kerry wrote.

“Seeing is believing. Many of us who once believed civil unions were sufficient to protect legal rights because we thought of marriage as a religious sacrament between a man and a woman, have seen that no church has been forced to do anything that contradicts its teaching. But when two committed people apply for a Massachusetts marriage license, they are equal whether they are gay or straight. It's not about a word – it's about equality under the law.”

Kerry added that it was time for Congress to repeal the Defense of Marriage Act (DOMA), the 1996 law that bars federal agencies from recognizing the legal marriages of gay couples.

“Is this a journey for all of us?” Kerry concluded. “Yes – and appropriately so, because it's a journey for our country. And although it sometimes takes too long, America always ends up on the right side of history.”