WASHINGTON >> Donald Trump pleaded Friday with Christian conservatives to rally to his candidacy, but in a high-profile speech to evangelicals made no mention of issues of central importance to them, such as abortion, same-sex marriage and Israel.

“You didn’t vote four years ago,” Trump said in an address at a conference convened here by the Family Research Council, warning, “this is your last chance, this is it.”

He appealed to the attendees with biting attacks on Hillary Clinton and a vow to promote religious freedom and appoint conservative judges — holding up the late Justice Antonin Scalia as the “ultimate example of what we’re looking for.”

It was a somewhat unusual appearance for a Republican presidential nominee less than two months before the election. Most candidates are by this point seeking to find and persuade undecided voters, not beseeching the most loyal party activists.

But Trump, a twice-divorced casino operator who has boasted of his sexual exploits, is no typical Republican nominee. And it is an open question whether he can count on the votes of the sort of social conservatives who at this time in the campaign are usually hard at work volunteering for the party’s standard-bearer.

So Trump, once a regular Howard Stern guest and a Playboy cover boy, momentarily stepped away from the swing states that will decide the presidential race and ventured into the basement ballroom of a Washington hotel to make his pitch. He lamented how difficult it is to raise Christian children today, quoted from Scripture and revealed a bit of news that illustrated how focused he is on turning out core Republican voters. He would, he announced to applause, travel to St. Louis on Saturday to attend the funeral of Phyllis Schlafly, the longtime conservative warrior who died this week at 92.

Trump was warmly, if not rapturously, received at the annual conference, which is billed as the Values Voter Summit, and displayed a measure of self-awareness. After pledging to undo restrictions on religious liberty, he joked, “I figure that’s the only way I’m getting to heaven.” And he received an ovation after vowing to defend what he termed America’s Christian heritage.

But this was not exactly Trump’s natural habitat, and what was absent from his speech underscored why he would be compelled to speak to a Christian conservative audience so late in the campaign.

He is ill at ease discussing the issue of abortion — and avoided it entirely when he accepted the presidential nomination in Cleveland — and has been vocal about his hopes that Republicans can win the support of gay voters. And his unfamiliarity with evangelical Christianity makes it hard for him to articulate the importance of defending Israel.

“Support for Israel now rivals the abortion issue in the political lexicon and the hierarchy of issue concerns of evangelical voters,” said Ralph Reed, a longtime conservative Christian leader, who had wanted Trump to incorporate talk of the Holy Land into his stump speech. “They will not support a candidate that in their view does not support the state of Israel.”

Trump is, however, comfortable speaking in pugilistic terms and making sport of his rivals. Veering away from cultural matters, he used his speech to belittle Clinton’s foreign policy record and promise a vigorous attack on Islamic terrorism. Without reiterating his praise this week for Vladimir Putin, Russia’s strongman president, Trump said he would gladly work with Russia to take on the Islamic State. “If they want to join us on knocking out ISIS,” he said, “that is just fine as far as I’m concerned.”

The Islamic State aimed to destroy “what it calls the nation of the cross,” Trump said, pointing directly at his audience as he spoke.

And days after Clinton said that Islamic terrorists were praying for Trump’s victory, Trump fired back the same accusation. “Boy, would they dream of having her as president,” he said of the Islamic State.

Trump also accused the Obama administration of doing a poor job of accepting Christian refugees from Syria (though he has proposed a total halt to the admission of Syrian refugees.) Such talk and, even more important, the unpopularity of his Democratic opponent on the right, has helped nudge some skeptical evangelicals in Trump’s direction.

But many in attendance here acknowledged that Trump is the most secular Republican presidential nominee in recent times. And they were quick to acknowledge that some Christian conservatives still are not ready to cast a vote for somebody who does not share all their values. Some doubters are even in their own families.

“My son-in-law,” said Susan Parker, an attendee from San Antonio who has rallied behind Trump. “He’s a Republican, but he’s a Christian first. He said, ‘I’m looking at the qualifications of a good leader, and he does not qualify.’”

It is those voters who explain why Trump is still only receiving the support of slightly more than 80 percent of those who identity as Republicans, according to polls. Boosting that number, Trump’s aides explained after his speech, is why he made the trip to Washington. Trump has sought to ease conservative discomfort with vows to appoint conservative jurists. And he selected a steadfast Christian conservative, Gov. Mike Pence of Indiana, as his running mate.

But Trump has largely declined to push the issues that have defined the Christian right for decades. In doing so, he has effectively wagered that evangelicals care more about combating political correctness and safeguarding America’s traditional cultural identity than resisting the tide of what they perceive as sexual permissiveness.

As a result, he has ceded the public debate on much of the culture war to Democrats, who have campaigned with enthusiasm as a party supportive of gay rights and opposed to restrictions on abortion.

The stakes are high for both Trump, who would struggle to win the presidency without the overwhelming support of evangelicals, and religious conservatives, whose political agenda has failed to gain traction during the eight years of the Obama administration.

Trump has gone to great lengths to win over evangelicals well after securing the nomination. He recently attended a meeting of evangelical pastors in Florida, and he hosted an hourslong gathering of Christian conservatives late in June.

Gary Bauer, a prominent Christian activist who ran for president in 2000, said that Trump was plainly an imperfect fit with the conservative faith community. Bauer predicted that in the end, reticent conservatives would come around to support him as the best available candidate.

“This constituency prefers people that have followed various moral guidelines on a variety of issues,” Bauer said. “But at the end of the day, you’re not getting a Sunday school preacher here, or a pastor. You’re picking a president.”

David Lane, a social conservative activist who has advised several presidential candidates, said the selection of Pence was taken by religious conservatives as a friendly signal from Trump.

But Lane said he wished Trump would “do more on the evangelical and pro-life Catholic issues” on the campaign trail. In an email missive to his political organization earlier this summer, Lane argued that conservative Christians should support Trump as an alternative to Clinton, but acknowledged he was a cipher on important issues.

“What and how will Mr. Trump do?” Lane wrote. “I don’t know.”