WASHINGTON -- When a coalition of mayors launched a campaign to push for marriage equality a month ago, there were about 70 individuals signed on to it. Now, there are 153 involved in Mayors for Freedom to Marry, with the Republican mayor of one of the nation's largest cities serving as a co-chair.

"This is an equality issue, nothing more, nothing less," San Diego Mayor Jerry Sanders (R) told The Huffington Post during a sit-down interview on Wednesday. "History is going judge us 10, 20, 30 years from now. I think it's going to be very different then. We're seeing the landscape change dramatically."

Sanders is one of just four Republicans signed on to Mayors for Freedom to Marry. The others are Mike Gin of Redondo Beach, Calif., Dennis O'Brien of Newton, Pa., and Craig Cates of Key West, Fla. Sanders said that while his party's involvement is small so far, he is confident that there are Republican mayors -- especially in smaller cities -- who will eventually come out for marriage equality.

Sanders' coming out, if you will, took a significant amount of political courage. After he announced his support for marriage equality in 2007, fighting tears at a news conference, the local Republican Party threatened to take away its endorsement of him.

"They were ready to tar and feather me," said Sanders, whose daughter is a lesbian.

In fact, it is this personal connection to the LGBT community that Sanders said he believes will shift the Republican Party to endorse equality.

"The courage of people who have come out has really changed the landscape," Sanders said. "When people are in the closet, nobody ever knew any gays or lesbians, or didn't think they did. Pretty easy to demonize someone like that. When it's your family, when it's your friend, when it's a coworker or someone you know and respect, all of a sudden you realize they're just like we are."

Sanders declined to comment directly on what he thinks of the GOP presidential candidates touting their opposition to same-sex marriage on the campaign trail, but he did say, "I would hope the GOP would become a party that welcomes people from all walks of life and not exclude anybody, and I think that's one of the problems we've had. In the not so recent past, we've excluded large groups of people with the rhetoric that gets going in the campaigns."

He also added that he gets frustrated when politicians tout the so-called "traditional family" as arguments against marriage equality and same-sex adoption.

"I love those arguments," he said sarcastically. "Traditional families bring great upbringing, great values. Traditional families bring mediocre upbringing and values. And traditional families bring child abuse, sex abuse, beating. I mean, it runs the gamut, and I would suspect, it would be the same no matter who the family is. I think that a committed couple can love a child every bit as much as a heterosexual couple."

Republican politics have changed significantly in San Diego since Sanders spoke out in 2007. This year, there are two openly gay candidates running for the Republican mayoral nod in San Diego. Sanders is being forced out by term limits.

And though of a different political party, Sanders said he would really like to see President Barack Obama finally evolve and support marriage equality.

"He's the leader," he said. "I think that that's something the president needs to do."

Watch Sanders' 2007 press conference: