A prominent advocate for the irreligious says there are at least 30 "closeted" members of Congress who don't believe in God, and that he hopes a California congressman's Thursday admission of disbelief will encourage others to come forward.

The advocate, an advisory board member of the Secular Coalition for America, has for more than a decade plied private admissions of atheism from members of Congress with the promise of confidentiality, and said Rep. Jared Huffman, D-Calif., is in good company.

Huffman said in an interview published Thursday that “I suppose you could say I don’t believe in God,” though he's uncomfortable with the certainty the word "atheist" implies.

“People are not ashamed, it's a political issue soley," the Secular Coalition member told the Washington Examiner.

"The largest number was 42," the board member said. "While I have no specific knowledge, I am sure the number is significantly higher than those I know.”

Currently, more than 30 of the 535 voting members of Congress do not believe in God, the advocate said, though he said his work is nonscientific and doesn't include the newest members. The headcount includes members of both parties, he said.

If lawmakers are reflective of national demographics, there would be about 59 nonbelievers in Congress.

A 2016 Gallup survey and a 2014 Pew survey both found 11 percent of Americans do not believe in God. Perhaps explaining part of the gap between the public and lawmakers, atheism is more common among young people.

Leaders of advocacy groups for people without religion say it’s important for politicians to identify themselves to help break lingering stigma.

Americans tell pollsters that they would be more comfortable voting for a gay or Muslim presidential candidate than an atheist. And as of 2014, 49 percent of Americans said they would not want a family member to marry an atheist.

“When people came out as gay, it changed the world for the GLBT community,” the advocate said, expressing optimism that Huffman’s admission will “stimulate more people to come out of the closet.”

The secular advocate uses the term nontheist, rather than atheist. There’s an argument that agnostics are by definition atheists, but using nontheist sidesteps the distinction.

Before Huffman’s announcement, only one sitting member of Congress, former Rep. Pete Stark, D-Calif., publicly said they were an atheist, in 2007. After he left office, Rep. Barney Frank, D-Mass., also acknowledged his atheism.

Some sitting members of Congress do identify their religion as “none” — notably, Rep. Kyrsten Sinema, D-Ariz. — or unaffiliated.

Rep. Jamie Raskin, D-Md., calls himself a humanist, but says he’s also Jewish.

Ron Millar of the Freethought Equality Fund PAC said the group would like more members of Congress to identify themselves as not believing in God.

“They just need a little encouragement,” Millar said. He said the fact that Huffman’s admission wasn’t a major news story may spur more disclosures.

“We don’t want to push people to come out,” he said, but “the demographics are behind us and the culture is changing.”