America's religious landscape is undergoing a dramatic change. According to a new national survey, the number of Americans who identify as Christians has dropped, while the ranks of those who don't identify with any religion have grown dramatically, leading some to wonder how these changing demographics will affect the political landscape.

The number of religiously unaffiliated Americans has grown to about 56 million, greater than Catholics and mainline Protestants and second in size only to evangelical Protestants.

That's according to the Pew Research Center's newest report, "America's Changing Religious Landscape," which outlines a shifting religious composition that may have significant impacts on US politics, culture, and society.

While the majority of Americans – about 7 in 10 – continue to identify with some branch of Christianity, the percentage who describe themselves as Christians has dropped nearly eight points, from 78 percent in Pew survey in 2007 to 70 percent in 2014.

And as the number of Americans who identify as Christians shrinks, the number who call themselves atheist, agnostic, or unaffiliated has grown nearly six points, from 16 percent in 2007 to almost 23 percent in 2014.

"This report shows a dramatic increase in the number of unaffiliated Americans," says Douglas Jacobsen, professor of church history and theology at Messiah College in Mechanicsburg, Penn., in a phone interview. "I'm surprised at how large that [change has been] in seven years," he said, adding that this is part of a 20- to 25-year trend that has slowly changed American politics.

Will declines in the number of religiously affiliated Americans hurt the Republican Party?

As The New York Times points out, "Republicans ... have traditionally relied on big margins among white Christians to compensate for substantial deficits among nonwhite and secular voters."

For example, it reports that in 2012, Republican nominee Mitt Romney received 79 percent support among white Evangelicals, 59 percent among white Catholics, 54 percent among non-Evangelical white Protestants, but only 33 percent among nonreligious white voters.

"The declining white share of the population is a well-documented challenge to the traditional Republican coalition, but the religious dimension of the G.O.P.’s demographic challenge has received less attention," writes the Times.

It's a threat that may not impact the party significantly now, but may have serious ramifications in the future, Joshua Weikert, assistant professor of political science at Albright College in Reading, Penn., says via e-mail.

"The bottom line, in my view, is that secularization may look more politically meaningful than it actually is, in the short-term – say, the next three to four election cycles – but that the longer-term implications are threatening to the Republican Party's recent trend towards a greater focus on social conservatism than on fiscal conservatism.”

That's because white evangelical Christians, who typically take a conservative stance on social issues such as gay marriage and abortion, have traditionally been a loyal voting bloc for the Republican Party, while the Democratic Party has positioned itself as a party for minorities and nonbelievers, in addition to people of faith.

While the number of Evangelicals hasn't changed much, the number of unaffiliated Americans has, and they are becoming increasingly organized and vocal in their campaign to keep religion out of public life.

"I do think this will make it harder for coalition building," says Professor Jacobsen, who adds that the spectrum of religious differences is now broader than in the past. "It's probably harder to build a coalition against theological lines," he says, predicting more political gridlock.

Nonetheless, according to Jacobsen, conservatives are taking note of the change, which is reflected in their language.

"There is less language about a Christian America, a slow moderation in language of how America describes itself," he observes.

And that may explain why some conservatives have now accepted gay marriage and are becoming more accepting of traditionally progressive issues like marijuana legalization.

As the population ages, the trend will likely grow more pronounced – the median age of unaffiliated Americans is 36, while the median age of Protestants is 52.

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But, "it's more complicated than just a secular versus religious divide," says Peter Ellard, director of the Reinhold Niebuhr Institute of Religion and Culture at Siena College in Loudonville, N.Y. "There are millions of Americans, especially young Americans, who want to be spiritual without being religious ... They are going to increasingly come into the national political conversation. However, they will not be a single hot button issue group and they will not be a unified group."

"So what we are looking at is a very unstable and less predictable near-term future with regard to the national effects of these trends."