(Bloomberg) —As Donald Trump tries to build the kind of coalition that could win him the White House, he’s trying to master a tightrope walk with evangelical Christians who helped fuel his rise to the top of the Republican Party but could also limit his general-election appeal.

Several religious conservatives said Thursday they’ll be listening closely to what Trump says Friday at the Western Conservative Summit, a gathering in Denver sponsored by Colorado Christian University. He’s delivering remarks at 12:30 p.m. Eastern time.

Trump, who sparked a furor in March by saying if abortion was illegal there’d have to be “some form of punishment” for women who have them, is trying out a different approach on socially conservative issues: sharing his thoughts privately with evangelical leaders, rather than broadcasting them to the much wider audiences he commands as he campaigns for president.

The presumptive Republican nominee took three days to comment publicly on the Supreme Court’s decision to strike down Texas abortion clinic restrictions on Monday, a ruling that ignited social conservatives across the nation.

When a radio host asked him about the ruling on Thursday, he said the outcome would have been “the opposite” if he were president — because he’d appoint conservative justices. At a town hall event in Manchester, New Hampshire, on Thursday afternoon, Trump passed on a chance to expand on his views when an anti-abortion supporter took the mic. “We’re all with you,” Trump simply responded.

After the ruling on Monday, Trump spoke privately with the campaign’s Executive Evangelical Advisory Board, reaffirming his commitment to appointing pro-life justices, according to people familiar with the conversations.

“We take him at his word,” said Pastor Frank Amedia, a member of the advisory board.

But some Christian conservative leaders say they want Trump, who has a reputation for sliding from one position to another, to keep repeating his stances in public, as many times as possible. That also includes voicing support for traditional marriage and religious liberty. He doesn’t have to transform into a fiery minister, but he shouldn’t show the kind of reticence about social issues that Senator John McCain or Mitt Romney displayed during their general election campaigns, they said.

“There are still a lot of people wondering where he’s at on a lot of issues, so he still has to define himself,” said Saul Anuzis, a veteran of Ted Cruz’s campaign, which competed with Trump for the evangelical vote. “There’s this false assumption that people should line up behind him just because he’s the nominee. Those of us who are more traditional conservatives still have questions.”

If Trump doesn’t lock down the support of Christian conservatives by playing to their issues on Friday in Colorado and in the coming weeks, some Republicans won’t feel motivated to work hard to get him elected, Anuzis said.

As a matter of electoral math, Trump needs evangelicals as much now as he did in the primaries. He can’t win with them alone, but he can’t win without them, either.

“In a lot of ways, this is not so much a race about demographics as previous elections. It’s about ideology,” said pollster J. Ann Selzer.

In the last Bloomberg Politics national poll in June, conducted by Selzer, Trump received 54 percent support among evangelical Christians, while Clinton gets 36 percent from that group.

Trump will need a huge advantage against presumptive Democratic nominee Hillary Clinton with conservative evangelicals or another group in order to offset deficits with several other voting blocs, she said.

“It’s hard to see that he is the conservative Christian candidate this constituency has been hoping to elect to the White House,” Selzer said. “He’d need a lot more enthusiasm from this group to ensure they turn out and check the box next to his name in the voting booth.”

Asked how Trump reassures conservatives about his positions on issues such as abortion without losing ground with voters in the center, Republican pollster Kellyanne Conway, one of Trump’s new senior strategists, said he would work to shift the spotlight to Clinton.

“Mr. Trump could force a two-way conversation on abortion and upend the free pass that Hillary and the Dems get on the issue,” Conway said. “Trump’s opponent is an unapologetic extremist on abortion who allows for no exceptions or reasonable regulations on abortion whatsoever. She and her party’s platform essentially say ‘abortion for anyone anytime anywhere.’ They should be forced answer a question about their lack of exceptions to abortion on demand.”

Trump aides said he’s likely to stress his plans for Supreme Court nominees during his remarks at the conservative summit Friday. It’s a good strategy, said Brad Todd, who was a senior adviser to former Louisiana Governor Bobby Jindal’s 2016 presidential campaign.

“The most potent selling point with religious conservative is an empty chair at the Supreme Court,” said Todd. “Evangelicals know that the secular Hollywood left will move us 30 years towards European cultural rot with a new Supreme Court justice picked by Hillary Clinton.”

United in Purpose CEO Bill Dallas, who organized a closed-door meeting between Trump and about 1,000 evangelical conservatives in New York last week, said he surreptitiously watched Trump as he stood backstage. Trump was quiet and patient, listening carefully while former presidential contender Ben Carson, the Rev. Franklin Graham and Liberty University president Jerry Falwell Jr. spoke, Dallas said.

“He was present. It wasn’t just that he was physically present, he was present,” Dallas said.

Trump then gave a speech Dallas thought was “amazing.”

“If he doubles down on talking with Christians about things in his heart, he’s going to mobilize Christians in a way that’s never been done before, I’m telling you. He’ll be our guy,” Dallas said.

There are some issues where a candidate can’t play both sides, and Trump needs to be blunt on those in public, he said.

“But if he shows the gentle side, the compassionate side, the person that’s going to fight for all Americans–if we start seeing his heart more, he’s going to draw all the sides,” Dallas said.

—With assistance from Terrence Dopp.