Brian Brown, president of the National Organization for Marriage (NOM), argues that “our system of government is at stake” in the gay marriage debate.

Under Brown's leadership, NOM has expanded beyond opposing gay nuptials to lobbying against the rights of LGBT people. The group has endorsed an effort to repeal a law approved by California lawmakers that gives transgender K-12 students certain rights. And it was revealed last week that Brown personally testified in favor of a Russian bill that prohibits foreign couples living in countries where same-sex marriage is legal – the U.S. included – from adopting Russian born children.

(Related: NOM's Brian Brown testified in favor of Russia's ban on gay adoption.)

Brown appeared Monday on The Janet Mefferd Show to discuss NOM's recent lawsuit against the IRS over an alleged leak by the government. Last year, the Human Rights Campaign (HRC), the nation's largest LGBT advocate, posted online a redacted version of the group's 2011 Form 990.

The document revealed that 75 percent of NOM's contributions ($4.7 million) came from just two sources. However, the identities of the donors were not revealed.

In posting the document, HRC said that NOM had made it available “after HRC requested the documents in-person at their Washington, D.C. office.” Many non-profits make such documents available to the public upon request.

Maggie Gallagher, the group's chairwoman at the time, independently corroborated the story in May: “You may recall that a low-level employee also released NOM's private tax-return information to a guy claiming to be a NOM employee, who then posted it on the Internet,” Gallagher wrote.

Chairman John Eastman has blamed the disclosure for mounting losses at the ballot box.

“The campaign of harassment and intimidation that had been tried and perfected in the fight over California's Proposition 8 could now begin again in the 2012 election cycle,” Eastman wrote. “That effort succeeded. Donations to NOM and to the ballot campaigns then underway became increasingly hard to come by, to the point that the same-sex marriage forces were able to outspend NOM and its allies by more than $20 million dollars (a nearly 4 to 1 advantage) in the 4 States where marriage was on the ballot in November 2012, resulting in the first electoral losses for traditional marriage ever.”

Brown and Eastman both claim that the IRS leaked the document.

“Everything is at stake in this fight,” Brown told Mefferd. “I think people are starting to wake up to the fact that even our system of government is at stake here. If you've got, in California, for example, voters who are told by our highest court that if the governor and attorney general don't agree with them, 'too bad, you don't get representation at the Supreme Court.' That strikes to the heart of what type of government we have. Whether this is the representative republic or not. In the same way, if the government itself and its agencies get to begin targeting those of us that believe marriage is the union of a man and a woman, we're in for big trouble.”