The nation's most vocal opponent of gay marriage has opened an office in the nation's Capitol to fight for DOMA.

The National Organization for Marriage (NOM) has been vociferous in its opposition to gay marriage victories this spring in Maine, Vermont and New Hampshire.

The group says it will use its D.C. office to “stop any attempt to repeal the Defense of Marriage Act (DOMA) that may come through the courts or lobbying in Congress.”

DOMA is the 1996 law that defines marriage as a heterosexual union for federal agencies and allows states to ignore legal gay marriages performed elsewhere. The law bars legally married gay couples from accessing federal benefits such as Social Security.

There are currently four lawsuits challenging DOMA in the federal courts. It is highly likely one of the suits will reach the Supreme Court, where a win could possibly open gay marriage for the entire country, but a loss would set the movement back decades.

President Obama has said he supports efforts to repeal the anti-gay law, but his administration's continued defense of the law has angered gay rights groups.

“When the battle was to get a marriage amendment on the ballot in California, NOM was there to help. When Tim Gill and his friends decided to push gay marriage bills through [the] legislatures [of] blue states in the northeast, NOM lead the fight, helping to stop gay marriage in New York, working to overturn gay marriage in Maine, and helping win substantive religious liberty protections in Vermont and Connecticut,” Brian Brown, NOM’s executive director, said in a statement. “Now gay marriage advocates are pushing Obama for the penultimate prize: repealing the federal Defense of Marriage Act, the only national law that protects marriage. We felt NOM needed to be here in D.C. to make the voice of the majority heard.”

In New York, the Maggie Gallagher-led group has threatened to boot out Republican senators who vote in favor of a gay marriage bill waiting for Senate approval to become law. NOM announced last month it will use funds raised through its New York PAC to back primary challengers of GOP senators who do not support their anti-gay marriage position, and will reward Democrats who do.

In Maine, NOM has partnered with the Catholic Diocese of Portland to create the Stand for Marriage Maine coalition. The new group is organizing a “people's veto” to repeal gay marriage in the state.

NOM also played a pivotal role in passing Proposition 8, the anti-gay measure that yanked back the right to marry from gay and lesbian couples in California. A California gay rights group, Californians Against Hate, has alleged NOM is a political front group for the Mormon Church, whose members, under appeal from church leaders, donated enormous financial and organizing resources towards passage of Proposition 8.

Recently, the group invited Maggie Gallagher to take a lie detector test on the question of who's funding NOM.

“Maggie, you claim that the Church of Jesus Christ of Latter-day Saints (the Mormons) did not help establish, or give any money to your National Organization for Marriage (NOM), or to any of your other organizations, or even you personally,” the group says in a statement. “Let's find out once and for all, Maggie.”

When asked for comment, Californians Against Hate Founder Fred Karger said he was convinced the group was backed by the Mormon Church.

“I am continually amazed at how a two person organization like NOM can spend over $6 million to fight marriage equality in 6 states and now in Washington D.C.,” Karger told On Top Magazine in an email. “It leads me to believe that the Salt Lake City-based Mormon Church is funding and running the show. They must be using NOM as their front group in all these battles like they have done in the past.”