The American Humanist Association, a secular activist group, has said there are 24 members of the U.S. Congress who are secretly atheists.
Maggie Ardiente, director of Development and Communications for AHA, said at the World Humanist Congress meeting in Oxford that the United States is "really behind when it comes to humanism in politics."
She noted, however, that 24 members of Congress have "privately" admitted their non-theism she was quoted as saying in a report by Religion News Service.
"We already know of 24 members of Congress who have told us privately that they don't believe in God, but they won't come out, of course, and if we tried to out them they would deny it," Ardiente said.
Twenty percent of Americans say that they are atheists, but most people in the United States still prefer leaders who hold on to their religious beliefs.
In a recent Pew Research survey, 53 percent of Americans said they are least likely to choose a candidate who doesn't believe in God.
After U.S. Congress Democratic Party Representative Pete Stark of California lost his House seat in 2012, there were no openly atheist politicians in the U.S. Congress.
A few months after retiring, former Rep. Barney Frank announced his nonbeliever status, a declaration he made more than 25 years after coming out as the first openly gay member of Congress.
Frank said that he is more comfortable going public with his sexuality compared to revealing his nonbelief.
James Woods of Arizona has openly campaigned as an atheist. If he wins, he would be the first atheist to openly declare his beliefs.
"Americans have a much stronger civil religion and a much stronger sense of being a nation under God and chosen by God.
"It's a bit treasonable, unpatriotic, to reject religion," said Linda Woodhead, professor of sociology of religion at Lancaster University.
The American Humanist Association said that public distrust is not the only reason why atheists are discouraged for running from office.
A major setback lies in the fact that some states have outright laws prohibiting atheists from running for office.
"Whether we recognize it or not, Americans are held captive to the will of religious right leaders who remind us of our inferior position by using the power of government to enforce laws that put truth claims about religion in front of us at every turn," Ardiente said in a 2013 interview.