“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 Mr. 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.”

Mr. 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 Mrs. Clinton’s foreign policy record and promise a vigorous attack on Islamic terrorism. Without reiterating his praise this week for Vladimir V. Putin, Russia’s strongman president, Mr. 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,” Mr. Trump said, pointing directly at his audience as he spoke.

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

Mr. 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 Mr. Trump’s direction.

But many in attendance here acknowledged that Mr. 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 Mr. 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.’”