Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE faces a reckoning on Tuesday with top social conservatives and evangelical leaders at a high-stakes gathering in New York City.

The likely GOP presidential nominee will attend a meeting at the Marriott Marquis hotel in Times Square with some of the most influential Christian conservative leaders in the nation.

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Afterward, hundreds of social conservative activists from all parts of the country will quiz the candidate and explain their policy positions to him.

Both sessions will be closed to the media.

The event will allow faith leaders to “better understand [Trump] as a person,” while helping Trump to “better appreciate” the views of Christian conservatives, according to an invitation sent out by My Faith Votes, a socially conservative group aligned with former GOP candidate Ben Carson, who is now advising Trump.

For Trump, it is an opportunity to shore up a segment of the conservative base he will need in the fall if he’s going to be competitive against presumptive Democratic nominee Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE.

Some will arrive with serious apprehension that Trump can be a trusted advocate on causes important to them. They will seek reassurances from him before laying their credibility on the line.

“The challenge for Mr. Trump here is that these are not people who operate in a grey world. Everything here will be black and white,” said Southern Baptist Convention President Ronnie Floyd, who is on the steering committee for the gathering.

“We believe that the Bible is the word of God and that Jesus Christ is the only savior of the world,” Floyd said. “We believe the nation needs spiritual revival and that we must take the gospel to the ends of the Earth. We want a champion in the White House who will fight for religious liberty, and that’s why we’re having this meeting: to discern what he believes.”

The meeting was arranged by top Trump surrogates to the Christian community and by Christian luminaries not yet on board with his campaign, like Focus on the Family founder James Dobson, The Family Leader President Bob Vander Plaats and Family Research Council President Tony Perkins.

Trump has struggled to convince many leaders that he will be a trusted advocate.

Dobson, Vander Plaats and Perkins all supported Ted Cruz Rafael (Ted) Edward CruzVideo of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral Sunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Democrat on Graham video urging people to 'use my words against me': 'Done' MORE during the primaries and have yet to announce their support for Trump in the general election.

Penny Nance, president and CEO of Concerned Women for America, who is also on the steering committee for the event, is a case study for why Trump must win the support of these skeptical social conservatives.

Her group claims to have reached 2 million voters on a nationwide bus tour for Republican nominee Mitt Romney during the 2012 presidential election.

Nance says she will personally cast a ballot for Trump in November, but she hasn’t decided yet if he merits the kind of activism her group did for Romney in 2012.

“No one is laboring under the delusion that Donald Trump is a Bible-banging evangelical. Nobody thinks that,” Nance said. “The question is, what are his core values? I think that on a range of issues, we just don’t know yet. He’s sent conflicting signals.”

Among the issues conservatives hope to challenge Trump on: abortion, which Trump once supported but now says he opposes; Planned Parenthood, which Trump has defended; controversial rules such as the ObamaCare birth control mandate and transgender bathroom laws; and gay marriage, which Trump has said he opposes.

Some, like Nance, worry Trump is only paying lip service to their causes without fully grasping why those causes are important to them.

Others, who will not take part in the meetings, will actively protest the event.

Advocacy group Faith in Public Life has arranged a press conference outside the hotel with a half-dozen faith leaders from New York to “rebuke Donald Trump’s vitriolic, immoral rhetoric.”

Still, Trump has made some inroads with evangelicals recently.

Ralph Reed, founder of the Faith and Freedom Coalition, has emerged as one of Trump’s most prominent advocates.

“Hillary Clinton supports abortion on demand with U.S. tax dollars, wants to redefine marriage and appoint extremely liberal judges,” Reed told The Hill. “She supports the Iranian nuclear deal and the ObamaCare contraception mandate. I just ask that Trump be good on these issues, and as far as I’m concerned, he’s with us all the way.”

Many social conservatives were thrilled by the list of judges Trump put forth — with assistance from conservative groups — to fill the Supreme Court’s vacancy.

Trump also extended an olive branch to the Christian community last month by hiring anti-abortion rights advocate John Mashburn to act as his top policy adviser.

Mashburn joins a growing list of Trump advisers — including Sarah Huckabee Sanders, the daughter of former Arkansas Gov. Mike Huckabee — who give social conservatives a sympathetic ear inside the campaign.

And later this month, a group of Carson allies plans to launch a super-PAC meant to mobilize Christian conservatives.

Trump will rely on that network of evangelical supporters to maximize conservative turnout on Election Day.

“I had reservations once, too, but I’ve come around,” said Andrea Lafferty, executive director for the Traditional Values Coalition. “He’s not perfect, none of us are. But Hillary Clinton is a threat to this nation, so for those who are only begrudgingly going to this meeting, I’d say it’s time to get on board. The train is leaving the station.”