(CNN) The presidential race is shaping up to be a full-scale war for the soul of the Republican Party.

Christian conservatives have launched a fierce offensive against corporate leaders, and the attacks seem certain to intensify in the coming months as GOP presidential hopefuls work to prove their ideological bona fides.

Evangelicals have already lost several major fights this year, most prominently in Indiana and Arkansas, where Republicans -- facing furious condemnation from major businesses and LGBT activists -- had to backtrack on so-called religious freedom laws that critics warned would allow discrimination against gay customers. Religious leaders could suffer another setback this summer if the Supreme Court rules gay couples nationwide have a constitutional right to marriage, a move many major corporate leaders are hoping to see.

Christian activists are vowing to strike back and plan to use the 2016 presidential campaign to advance their cause. The White House bids of candidates like Sen. Ted Cruz of Texas and former Arkansas Gov. Mike Huckabee could give social conservatives a bullhorn to defend their priorities and turn 2016 into a referendum on the GOP's future.

Newt Gingrich, the former House speaker and 2012 presidential candidate, blasted corporate America for succumbing to cultural pressure to impose "whatever language and other requirements the gay community wants."

"Big businesses -- a lot of them are people who want to feel good when they go to their country club and want to feel like they've taken the socially correct position as defined by The New York Times," Gingrich said in an interview.

'Religious liberty'

The 2016 GOP candidates must "stand up for religious liberty" and point the finger at the "real bigots," Gingrich added: "The real bigots are the people who are saying, 'I deny you the right to freedom.'"

Richard Land, the former head of the Southern Baptist Convention's Ethics and Religious Liberty Commission, said the business community is increasingly holding hands with the "totalitarian wing of the left," deploying "bully boy tactics" to pressure Christians to abandon their deeply held religious convictions.

"Parts of the business community will continue to pander to the loudest voice until they meet opposition," Land said. "And they'd better be prepared to meet some opposition, because there are millions and millions of evangelical Christians in America and they have a choice about who they do business with."

Corporate leaders have chosen their words carefully, casting their defense of gay rights as a straightforward business decision rather than an attack on the ideological beliefs of Christian conservatives. It's a demonstration of how the community remains closely aligned with the GOP, and it makes the harsh words from Republican elected officials this year all the more striking.

This public assault on big business comes as major companies have become a powerful force in the debate on gay rights. A slim majority of Americans now back same-sex marriage and such unions are now legal in dozens of states. As the country grows increasingly accepting of gay rights, businesses are following suit.

When the Supreme Court heard arguments on the constitutionality of same-sex marriage last month, hundreds of companies, including powerful Wall Street banks such as Goldman Sachs, Bank of America and JPMorgan, signed a brief supporting it.

As Arkansas considered a religious freedom law this year, Walmart -- one of the state's largest employers -- pressured the governor and legislature to scrap the original version of the bill and redraw the legislation. After Indiana passed a religious freedom law, some of the country's most prominent CEOs, including Apple's Tim Cook and Salesforce.com's Marc Benioff, warned that it would be hard to do business with the state.

During a religious freedom debate in Arizona last year, the National Football League even considered moving the Super Bowl out of the state if a discriminatory bill became law.

Same-sex marriage

But the Republican Party has stood by a much more traditional view of same-sex marriage and religious freedom. A CNN/ORC International poll conducted in April found that a majority of Americans oppose laws that would allow businesses to refuse services for religious reasons. But 60% of Republicans said wedding-related businesses should be allowed to refuse services to gay couples.

Now, conservatives are fed up with what they call meddling from the business community -- and their presidential candidates seem to agree.

Cruz, the son of a pastor, had harsh words for the business community last month after Indiana Gov. Mike Pence called for changes to his state's religious freedom law, under aggressive pressure from big business.

"It is unfortunate that large companies today are listening to the extreme left-wing agenda that is driven by an aggressive gay marriage agenda," Cruz said in Iowa.

Huckabee, a Southern Baptist preacher who won the 2008 Iowa caucuses by appealing to evangelical voters, launched his second presidential campaign last week with a speech promising to take on forces that are "criminalizing Christianity."

At least two other Republicans exploring presidential bids are closely tied to conservative evangelical activists: former Sen. Rick Santorum of Pennsylvania, a Catholic who won the Iowa caucus in 2012, and Louisiana Gov. Bobby Jindal.

In an op-ed in The New York Times last month , Jindal lamented that in Indiana and Arkansas, large corporations had "joined left-wing activists to bully" public officials into turning their backs on religious liberty. "That political leaders in both states quickly cowered amid the shrieks of big business and the radical left should alarm us all," the governor wrote.

Exercising caution

Other likely candidates have been more cautious. Former Florida Gov. Jeb Bush and New Jersey Gov. Chris Christie, both viewed as candidates aligned with the establishment, have expressed some support for religious freedom laws, including the one in Indiana. But both also supported changing the Indiana religious freedom law to address concerns about discrimination.

Activists say GOP elected officials have to contend with the reality that support for LGBT rights is more mainstream than ever before.

"People realize that the sky is not going to fall if people have equal rights," said Todd Sears, a former investment banker and founder of Out Leadership , a group dedicated to promoting LGBT rights in the business world. "The people in the Republican Party that are so anti-gay are a minority."

Christian conservatives aren't the only GOP constituency to tangle with businesses in recent years. Small-government conservatives have clashed with major companies by opposing the reauthorization of the Export-Import Bank, raising the debt ceiling and extension of a federal terrorism insurance program.

But the issue of gay rights is an especially prominent point of strain. The division is particularly evident in Iowa, where the state's large evangelical community has effectively picked the winners of the last two Iowa caucuses.

Religious activists in the Hawkeye State say religious liberty will be one of the most important issues they watch as they screen Republican candidates. Backing down in the face of big business, they said, would be unacceptable.

Steve Scheffler, president of the Iowa Faith and Freedom Coalition , said GOP presidential candidates had better be ready to address what he called an "increasing threat" on religious liberty.

"Somebody needs to call a spade a spade and call it for what it is, and if they're offended, so be it," Scheffler said. "They need to address the religious liberty issue when they come to Iowa."

Bob Vander Plaats, the head of conservative religious organization The Family Leader , said it was time for religious conservatives in the GOP to "take back the party."

The debate on religious liberty will "separate the wheat from the chaff quickly," Vander Plaats said. "Someone who's not strong and demonstrates bold and courageous leadership on religious liberty -- there's no way they'll be our nominee."