Current disappointment is unlikely to translate into substantial or lasting opposition. And not all evangelical supporters have taken issue with Mr. Trump’s decision. Robert Jeffress, pastor of First Baptist Dallas and a prominent supporter of Mr. Trump, said he “happily” deferred to the commander in chief, and he praised Mr. Trump for carrying through on a campaign promise to end American involvement in Middle Eastern conflicts.

“Some evangelicals may disagree with the president’s decision,” Mr. Jeffress said, “but I guarantee you there is not one evangelical supporter of the president who would switch their vote and support Elizabeth Warren or Joe Biden over a Syria decision.”

Franklin Graham stopped short of condemning Mr. Trump’s policy outright. The evangelist said he communicated with the president or vice president — he would not specify which leader — about the troop withdrawal within the last 48 hours, and said he ultimately deferred to their determinations. He declined to give specifics of his conversation.

“There are so many other issues at stake here,” he said, listing things such as Turkey’s membership in NATO and U.S. military bases in the country. “It is a very hard decision.”