President Bill Clinton — the man who signed the Defense of Marriage Act in 1996 — offered a forceful argument to overturn the law that denies same-sex couples the privileges of marriage in an op-ed for the The Washington Post, titled “It’s Time to Overturn DOMA.”

The Obama administration has refused to defend the law, which has been ruled unconstitutional by four federal district and two appeals courts.

In March, the Supreme Court will hear the case of Edith Windsor, who was forced to pay estate tax on her wife’s inheritance, despite laws that exclude heterosexual married couples from paying such penalties.

Clinton believes the Court should rule in favor of Windsor and couples in the nine states where same-sex marriage is legal.

On March 27, DOMA will come before the Supreme Court, and the justices must decide whether it is consistent with the principles of a nation that honors freedom, equality and justice above all, and is therefore constitutional. As the president who signed the act into law, I have come to believe that DOMA is contrary to those principles and, in fact, incompatible with our Constitution.

Clinton explains that he signed that bill — which passed both houses of Congress with only 81 votes against — was an attempt to prevent a Constitutional amendment banning gay marriage.

“Although that was only 17 years ago, it was a very different time,” he wrote.

Clinton, like President Obama — who went from opposing same-sex marriage to saying he believes the Constitution should guarantee marriage for same-sex couples — has evolved.

But the GOP clearly hasn’t.

Gay groups are still not allowed to participate in the most prominent right-wing event of the year, CPAC — though birthers like Donald Trump are. The Republican Platform not only calls for a Constitutional amendment banning gay marriage, it wants to reinstate Don’t Ask, Don’t Tell, another Clinton-era compromise that banned admitted homosexuals from serving in the military.

The biggest problem for the GOP is that their stand on same-sex marriage hurts them with exactly the voters they need to woo to ever have a hope of winning a presidential election.

“A new Quinnipiac poll out today drives this home with striking clarity: It finds that gay marriage has far greater support among constituencies that are growing as a share of the vote than it does with the public overall,”The Washington Post‘s Greg Sargent reports.

“The poll finds that a plurality of Americans supports same sex marriage, 47-43. But dig into the internals and you find that the groups that increasingly make up the main pillars of the Democratic coalition support it in much larger numbers. Hispanics: 63-32. Young voters: 62-30. College educated whites: 59-32. White women: 50-40.”

The only people who oppose marriage equality? Republicans, non-college-educated whites, and evangelicals. Voters the GOP would win even if they nominated the conservative who best exemplifies the “sanctity of marriage” — the thrice-married Newt Gingrich.

The 17 years since Clinton signed DOMA have contained remarkable progress fueled by a patient but urgent gay rights movement. Because of that, President Obama became the first president to speak out for gay rights in his inaugural.

And Republicans need to be aware that he won’t be the last.

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