Tim Pawlenty has joined presidential hopefuls Michele Bachmann, Mitt Romney and Rick Santorum in signing NOM's anti-gay marriage pledge.

Brian Brown, the president of the National Organization for Marriage (NOM), told MSNBC host Thomas Roberts on Friday that Pawlenty, the former governor of Minnesota, had agreed to become the fourth candidate to sign onto his group's pledge.

“We are very excited that not only three, now a fourth candidate has signed on,” Brown said. “Tim Pawlenty, we got word last night is signing on.”

Brown went on to deny that marriage equality is a matter of rights: “[T]he notion that what you're doing by passing same-sex marriage is expanding rights is wrong. You're basically undermining the rights of those of us who believe that marriage is between a man and a woman.” (The video is embedded in the right panel of this page.)

During a Christian Broadcasting Network (CBN) segment, NOM board chair Maggie Gallagher took a swipe at Pawlenty for refusing to sign the pledge.

“The big question is really what's going to happen with Governor Tim Pawlenty, who explicitly declined to sign NOM's marriage pledge this week,” Gallagher said. “We're hoping the governor changes his mind, because we think it's pretty peculiar for Governor Pawlenty, who's been a champion for marriage in Minnesota, to refuse to do the same for the people of America.”

Candidates that sign NOM's 5-point pledge promise to support a federal constitutional amendment banning gay marriage, defend the Defense of Marriage Act (DOMA) in court, appoint judges and an attorney general who will “respect the original meaning of the Constitution,” appoint a presidential commission to investigate the “harassment of traditional marriage supporters,” and back legislation that would allow a ballot question on the issue for voters of the District of Columbia.