Nov. 9, 2012 -- Tuesday's election brought some religious firsts for Congress, with a victory for Tulsi Gabbard, who will be the first Hindu congresswoman, and Mazie Hirono, the first Buddhist senator. Both are Democrats from Hawaii.

For a country whose founding principles include religious freedom, the American government has a history of being almost homogenous with respect to religion. For most federal representatives, the question isn't whether or not you're Christian but what Christian denomination you follow.

Half a century ago it was almost unthinkable for some that a Catholic could win the presidency.

But just as leaders have broken racial and gender barriers over the years, so too are non-Christian candidates moving forward.

Former Deputy Historian for the House of Representatives Fred Beuttler pointed to the 110th Congress, elected in 2006, as a win for religious plurality. That's the year a Muslim, Keith Ellison, D-Mich., and two Buddhists, Hank Johnson, D-Ga., and Hirono from Hawaii, were elected to the House.

Hirono is now leaving her House seat to become a senator. Tulsi Gabbard will succeed her.

"Tulsi never ran as a Hindu or thought of the campaign in that way," Gabbard campaign spokesman Jim McCoy said in an email. "However, after her victory there was a huge outpouring of joy and elation from Hindus throughout America and even in India. So although Tulsi has never seen it as a 'victory for Hindus,' it's clear that Hindus in America now feel less marginalized than they had prior to her election."

Beuttler attributed the changing makeup of the government to religious changes in the American population.

"The House is a very representative institution by its design," Beuttler said. As Americans become more diverse, "you expect to see more religious diversity in the House."

Luke Harlow, a historian of religion and political culture in 19th century America who teaches at the University of Tennessee, Knoxville, said an influx of immigrants from more religiously diverse areas in the 1960s gave rise to a less Protestant-focused electorate, but he did not think this week's victories for non-Christian candidates were representative of the national climate.

Hawaii, Harlow said, has a different geography and history from the continental U.S., which allows for more religious diversity.

"From an academic standpoint what has long been the case is that you've had a de facto moral establishment -- which has everything to do with the nature of American democracy -- that for many people feels very Christian, especially for outsiders," Harlow said, referring to Americans who fall outside the category of mainstream Christianity.

Harlow said there's no real reason to believe that a Buddhist candidate running for president "would get very far," even though there is no law keeping Christians in the highest office in the land.

Article Six of the U.S. Constitution includes the guideline, "no religious test shall ever be required as a qualification to any office or public trust under the United States."

"But culture is not just enshrined in law. It's a bigger concept than that," Harlow said.

Another candidate in the 2012 elections, Democrat Kyrsten Sinema of Arizona, has been described as an atheist or nontheist.

Sinema is not an atheist; she simply does not belong to any organized religion. After the initial count she had a lead of 2,700 votes over her Republican opponent. As of Thursday, there were still an estimated 631,274 early and provisional ballots to be processed in Arizona. If Sinema wins, that would make her one of a handful of non-affiliated representatives in Congress.

Roy Speckhardt, executive director of the American Humanist Association, said nonreligious people are becoming an important part of the American electorate as their numbers "skyrocket."

The Pew Research Center reported in October that one in five American adults described themselves as having no religious affiliation, up from about 15 percent in 2007. The percentage of Christians dropped from 78 percent to 73 percent over those years.

"The plethora of different types of religious belief that we're starting to see in the electorate, as well as in Congress, as well as other offices, is so important because it helps people realize that this isn't a Christian nation," Speckhardt said. "It never really was, but that is becoming a lot clearer today."

During the campaign, Congresswoman-elect Gabbard took some heat for her religion. In an interview on CNN, her opponent said her beliefs don't align with the U.S. constitution. But McCoy said Gabbard refused to get caught up in that issue.

Now that the race is over, Gabbard is still directing the public away from her personal beliefs.

"While I understand all of the interest about my being the first Hindu elected to Congress, I feel that of greater importance is the fact that Tammy Duckworth and I will be the first women combat veterans ever to serve in Congress in our country's history," Gabbard wrote to ABC News in an email. "Thousands and thousands of women in our armed forces have given their lives and made tremendous sacrifices, so to have the voice of women combat veterans in Congress is a very important milestone."