President Obama may say that his position on gay marriage is “evolving,” but top members of his administration are coming out with full-throated support of what progressives now call “freedom to marry.”

First came yesterday’s admission by Vice President Joe Biden, when he said, “I am absolutely comfortable with the fact that men marrying men, women marrying women and heterosexual men and women marrying are entitled to the same exact rights.”

Then, this morning, Secretary of Education Arne Duncan — an old Chicago basketball buddy — told MSNBC’s “Morning Joe” that he supported gay marriage.

While activists and many on the left are frustrated that the President won’t totally support same-sex marriage, the issue is proving to be an even bigger minefield for Republicans as Mitt Romney tries to shift away from the social issues that ended up dominating the primary and towards the economic issues that would allow him to appeal to the center.

But the conservative base won’t let him move on. Tomorrow, North Carolina will vote for a constitutional ban on gay marriage and civil unions — the primary turnout is expected to be heavily Republican, and it comes a blot on the Republican record as Democrats prepare for this summer’s convention in Charlotte. Bill Clinton has already weighed in with an automated call, asking voters to stand up for gay rights, warning that a ban would hurt the swing state’s image and economy.

“What it will change is North Carolina’s ability to keep good businesses, attract new jobs, and attract and keep talented entrepreneurs,” he says. “If it passes, your ability to keep those businesses, get those jobs, and get those talented entrepreneurs will be weakened.”