As the GOP establishment slowly coalesces around the presumptive nominee, the foot soldiers of the movement face an agonizing dilemma: whether to line up behind a candidate many members view as a ideological heretic or to stay true to their principles and reject him -- even though doing so could help Hillary Clinton claim the White House.

The self-reflection is particularly acute for members of the influential Council for National Policy, an umbrella network of conservative activists -- the membership of which has been largely secret but can now be exclusively revealed to a greater extent than ever before by CNN.

The Council was founded in 1981 by Tim LaHaye, the evangelical minister best known for the "Left Behind" series of prophesy-infused fiction books.

Uniting social, fiscal and religious conservatives, the CNP, nicknamed "The Group," has prided itself for years on promoting conservative values and helping grassroots conservatives outside the GOP structure to coordinate and share ideas and information. Its membership is a powerful organizing force behind conservative candidates and has helped to cement the movement's aspirations deep in Republican Party ideology.

A copy of the organization's membership list and directory obtained by CNN shows it mixes prominent conservative leaders like Brent Bozell III and Phyllis Schlafly with a smattering of former presidential candidates, business leaders and social activists. The group rarely courts publicity, but its members will be crucial in determining the amount of buy-in from social and evangelical conservatives for Trump's national campaign.

Trump starts from a position of weakness among CNP members, and the choice is particularly galling for some social conservatives because the 2016 election had seemed to offer the chance of nominating a candidate -- like Ted Cruz or Marco Rubio -- who was squarely in line with their core philosophy.

Tony Perkins of the Family Research Council currently heads the executive committee of the CNP, and told CNN in an interview that Trump's takeover of the Republican Party is posing searching questions for the conservative grass-roots.

He said it is incumbent upon Trump to reach out with tangible steps to quell anxiety in the movement if he is to ensure a strong GOP turnout in November.

"Many conservatives want to be able to be for Donald Trump because they fear the alternative, but they have not yet seen in him what they need to see to make the transition," Perkins said. "There is not a lot that has transpired since Ted Cruz left the race and Donald Trump has been on the path to being the nominee -- he has not done anything that would make people change their minds."

Another prominent member of the CNP is former Ohio Secretary of State Ken Blackwell, who said he is "slow walking" his embrace of the Trump candidacy. In some ways, Blackwell said, promoting Trump would for conservatives be akin to snatching defeat from the jaws of victory if he does not accept their principles, after generations of trying to put conservative thought at the heart of U.S. government.

"I would say everybody wants to unify and everybody is mindful of the fact and respectful of the fact that Trump has weathered the storm of a primary," Blackwell said. "But the vast majority of us are not ready to jettison our platform or the philosophy that has gotten us to this majority party status, the only other rung is the presidency."

Better than Clinton

Pragmatists among CNP members argue that while Trump may part with conservatives on many core issues -- including reining in the size of government, on opposing entitlement reform and in the often vulgar tone of his campaign, it is already clear he would be better for conservatives than the alternative -- Hillary Clinton.

Schlafly, a pioneering conservative activist and founding member of the CNP, said that Trump is not the first Republican candidate to face questions about his personal authenticity as a conservative.

"I can remember 1980 when a lot of us didn't think Reagan was an authentic conservative. Reagan turned out to be best president of the century," she said. She backed Trump partly because he was the only candidate talking about illegal immigration, which she said was "the most important issue in the country."

Father Frank Pavone, a Roman Catholic priest who directs the Priests for Life organization, is backing Trump because he believes in the sincerity of his anti-abortion rights credentials -- despite doubts among other conservatives on his conversion from a previously pro-abortion rights position.

"No matter what uncertainties there might be about him, there are no uncertainties about where Clinton will go or anyone on the Democratic side on this issue in particular," Pavone said.

"A lot of people will come out with the statement that she is as bad as he is, but he is not on this issue particularly," said Pavone, who believes that Trump's change of attitude on abortion is "real and sincere."

Pavone believes that now that Trump is the presumptive nominee and has a realistic chance of becoming President, he will moderate the antics and demeanor that have troubled many conservatives.

"From my own communication with people who have known, and worked with and advised Mr. Trump, I have got nothing but reassurance," Pavone said. "I really think that that principle that the office shapes the man is going to kick in very strongly."

Perkins suggests that the presumptive nominee could make some tangible moves to bring values voters along with him. One visible step would be to pick a vice presidential nominee who is trusted by evangelical and social conservatives.

"Is there someone that we will have a confidence in that has a track record because past performance in the best indicator of future performance," said Perkins.

Alternatively, Trump could reassure conservatives by enlisting a trusted member of the community, like Cruz to help vet his judicial nominees — an intensely acute matter for conservatives, given the open seat that belonged to late Justice Antonin Scalia. In fact, the open Supreme Court seat could emerge as substantial leverage for Trump to corral conservatives behind his campaign given fears in the movement that Clinton could select her own liberal nominee who could sit on the court for decades.

Trump may already be heading in that direction.

CNN's Dana Bash reported Friday that the billionaire told House leadership officials in a meeting on Thursday that he would produce a list of potential nominees in coordination with the Federalist Society and the Heritage Foundation.

But other CNP members are just not ready to make that leap of faith.

Kim Bengard, a businesswoman and social conservative activist from California, does not believe that Trump's conversion on abortion is genuine. After swallowing her reservations to side with previous moderate Republican nominees like Bob Dole, John McCain and Mitt Romney, Bengard has hit the end of the line with Trump.

"I can't do it," Bengard said, adding that she believes the billionaire's anti-abortion rights position is simply one of convenience.

"I don't believe he is a Republican. He is certainly not a conservative," said Bengard.

"I am going to in the end walk away with my convictions intact. I won't vote the top of the ticket, I am sad and horrified about what is ahead of us," Bengard said, adding she would restrict herself to down-ticket races in the current election season.

Inside "The Group"

CNP may be the most powerful group whose members you didn't know. As the group explains on its website, which provides no membership information, the CNP "brings together the country's most influential conservative leaders in business, government, politics, religion, and academia to hear and learn from policy experts on a wide range of issues."

The membership list is ''strictly confidential," a CNP memo obtained by The New York Times in 2004 noted. ''The media should not know when or where we meet or who takes part in our programs, before or after a meeting."

In 2014 and 2015, several GOP presidential candidates -- Cruz, former Gov. Mike Huckabee, Dr. Ben Carson, Sen. Lindsey Graham, Sen. Rand Paul, and former Sen. Rick Santorum, among others -- spoke with CNP members in the hopes of securing their support.

At the end of 2015, conservative activist leaders linked to "The Group" voted to support Cruz in the primaries but in February, as reported by the National Review ,members of the Group began expressing concerns about Cruz's viability. But the CNP itself says that it does not endorse candidates and does not hold straw polls showing presidential preference.

The ranks of members are made up of grassroots conservatives who, according to their Values Statement, "value the power of collaborative networking among conservative leaders to strengthen the movement and its impact."

CNN obtained a CNP membership directory from 2014, when Perkins was vice president of the executive committee and the president was Stuart Epperson, co-founder and chairman of Salem Communications. Secretary. Treasurer of the Group was John Scribante, Chief Executive Officer at Orion Energy Systems, Inc.

Several former GOP presidential candidates are listed, including Santorum, Gary Bauer, Herman Cain, Steve Forbes and Jim Gilmore.

The leaders of key conservative and like-minded groups are also on the roster, such as Citizens United President David Bossie, former Heritage Foundation President Jim DeMint, Tea Party Express Chairman Amy Kremer, National Rifle Association CEO Wayne LaPierre, Club for Growth leader David McIntosh, Judicial Watch President Thomas Fitton, Operation Rescue President Troy Newman, Americans for Tax Reform President Grover Norquist, and Jenny Beth Martin, co-founder of Tea Party Patriots.

Other boldfaced names, organizers and donors familiar in the conservative world include: Foster Freiss; Ralph Reed, Bishop E.W. Jackson, Ed Meese, former Reagan-era Energy and Interior secretary Don Hodel, Linda Bean, James Dobson, and Bain Capital Managing Director Louis Bremer.

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And the media world is represented. Listed on the 2014 roster are: Joseph Farah, founder and CEO of WND; Christopher Ruddy, Newsmax founder, CEO and president; and Neil Patel, co-founder of The Daily Caller.

The pursuit of the Group's goals is augmented by CNP Action, Inc., a sister organization that "promotes issues or specific pieces of legislation through regular publications and standing committee workshops," according to its website, and is headed by Gary Aldrich, the former FBI Agent whose 1996 book detailed accusations of security breaches at then-President Bill Clinton's White House.

The CNP's influence is beyond dispute. Reporter Marc Ambinder noted that shortly after "candidate George W. Bush spoke before a closed-press CNP session in San Antonio...magisterial conservatives pronounced the allegedly moderate younger Bush fit for the mantle of Republican leadership." (Ambinder allowed that the two moments might not have been directly connected.)

But while the impact of the CNP is clear, it is less certain that conservatives who have spent decades fighting to insert their ideology at the heart of government will present a united front in the coming fall election.

But for those conservatives who are still wavering about endorsing Trump or who might be tempted by a possible third party candidate, Schlafly, who has impeccable conservative credentials after a lifetime on the front-lines of the ideological struggle, has a simple message.

"I remind people we are a two party system. If you like a third party or some other way, you can move to Europe — You have got to pick one. The fight is in the Republican Party."