By Dan Merica, CNN

Washington (CNN) – This convention season has not been good for atheists.

The word "God" was reinserted in the Democratic platform after it had been removed. A plan to raise atheist billboards in the convention cities was stymied by opponents. And though there were preachers and rabbis and other religious leaders opening and closing each day of each convention, there wasn’t an avowed atheist talking up unbelief on either convention’s speaking list.

The political lockout has left many nonbelievers asking, “What political party represents me?”

“We are deeply saddened by the exclusion of a large number of Americans by both parties,” said Teresa MacBain, a spokeswoman for the group American Atheists, in an interview on Thursday. “It amazes me that in modern-day America, so much prejudice still exists.”

After word spread Wednesday that Democrats left God out of their platform, atheists rejoiced. “Truly amazing news,” wrote Loren Miller on Atheist Nexus, a popular atheist blog. “The Republicans remain in the firm grasp of right-wing Christian religiosity, and I really don't know what it's going to take to free them from it.”

But the convention committee immediately received huge pressure get God back in the platform. Even President Obama, according to CNN reporting, said, “Why on earth would that have been taken out?” when he first heard of the omission.

In an awkward session that required three voice votes on the convention floor, the Democrats opted to add “God” back to the platform.

For atheists, the Democrats were seen to be taking away a hard-fought victory. “We had 24 hours of joy as we felt (that) finally our government values all people,” said MacBain. “But that was short-lived. The vote last night angered many atheists and left them feeling excluded once again.”

Online, atheist websites and Facebook pages went from upbeat to downcast as news spread of the platform revision.

“Obama was the first president to acknowledge non believers,” Mark Musante wrote on the American Atheists’ Facebook page. “I wish he would stick to his guns.”

Musante was referring to Obama’s 2009 inauguration speech, when the president said, “We are a nation of Christians and Muslims, Jews and Hindus, and nonbelievers.”

Beverly Sitherwood, on the Friendly Atheist blog Facebook page, accused the Democrats of “Pandering for power.”

Some atheist leaders used the platform defeat as a rallying call.

“I guess a tiny step was too much to ask for,” David Silverman, president of the American Atheists, told CNN. “This was a clear message to the 16% of the voting population - we don’t count. Well, guess what, Dems - we do. And we vote.”

Silverman says that 16% of the voting public identify as nonbelievers. According to the Pew Forum on Religion and Public Life, 12% of the electorate in 2008 was made up of people with no religious affiliation, though experts say the number of avowed atheists is much smaller.

While acknowledging atheists, Obama has given platforms to high-profile religious leaders, including Rick Warren, a megachurch pastor who prayed at his inauguration, and Catholic Cardinal Timothy Dolan, who is giving the final prayer of the convention on Thursday night.

American Atheists’ plans to raise billboards ridiculing the presidential candidates’ faith ended in failure. After the group put up billboards in Charlotte, North Carolina, the site of the Democratic National Convention, last month, it quickly removed them due to “physical threats to not only our staff, but the billboard company as well.”

American Atheists had also planned on a billboard in Tampa, Florida, to coincide with the Republican National Convention there. But American Atheists said that all the billboard companies in Tampa rejected a sign taking aim at GOP presidential candidate Mitt Romney’s Mormon faith.

Perhaps because of the Republican Party’s ties to conservative Christianity, atheists tend to be Democrats. According to a 2012 Pew study, 71% of Americans who identified as atheist were Democrats.

“The Republicans who spoke at the RNC seemed more like televangelists than politicians,” MacBain said. “The message was clear from the RNC: Get God, or get out.”

The Republican’s 2012 platform mentions God 12 times, many of which describe the “God-given” rights that the Republican Party says are inherent to the American idea.

Though most atheist groups claim that there are closeted atheists serving as representatives and senators, only one has come out as such.

In September 2007, Rep. Pete Stark, Democrat of California, affirmed his atheism in a speech at the Humanist Chaplaincy at Harvard University.