People have been asking this question for decades, since at least 1989 when Mr. Graham, at 70, received a star on the Hollywood Walk of Fame. Two years later he was preaching in New York City’s Central Park before an estimated 250,000 people.

I asked this question recently of Lon Allison, author of a forthcoming book Billy Graham: An Ordinary Man and His Extraordinary God. Lon is an evangelical pastor and knows the Graham family well. He said, “Probably no one unless God so desires. A Billy Graham, a Martin Luther King, Jr., a Martin Luther, are called and gifted for a special calling in a special time. Billy, when asked that question while leading a global forum of evangelists from around the world answered this way: His arm swept out over the large gathering and simply said, ‘They will.’”

There has not been an evangelical Christian of recent memory with anywhere near the popular appeal of Mr. Graham. For a brief time, in 1989, there was talk of Franklin Graham filling his father’s shoes. Franklin began preaching occasionally at Billy Graham Evangelistic Association events. Then, it was Franklin, rather than his aging father, who prayed at the inauguration of George W. Bush in 2001. But people have not responded to Franklin in remotely the same way.

What is it about Billy Graham that seems so difficult to duplicate? For Mr. Graham, intangibles like personal humility and kindness translated across the television screen. There are other prominent evangelicals who have similar traits, such as Pastor Rick Warren, founder of Saddleback Church in California. He is the author of a book that sold more than 30 million copies, and he was once prominent enough that presidential candidates Barack Obama and John McCain came to his church for a presidential debate in 2008. But since then, there has been less interest in Mr. Warren as a public figure.

If I had to pick someone closest to being a Billy Graham today, it would be Rob Bell.

The most unusual thing about Mr. Graham’s success was the unlikely combination of personal appeal (looks, voice, reputation, likeability) with a message of sin and condemnation. He was able to point at millions and say, “You are a sinner,” and the millions kept watching and listening. Why they did not turn off their televisions, or stop going to those “crusades,” is the real mystery. However, the notion of a “next Billy Graham” must take stock of the fact that we do not watch television in the way we once did. Audiences are more segmented.

If I had to pick someone closest to being a Billy Graham today, it would be Rob Bell. A Wheaton College graduate like Mr. Graham, Bell is currently touring dozens of American cities making the case that “everything is spiritual,” his most common message. Mr. Bell was named by Time magazine as one of the “100 Most Influential People in the World” in 2011, before he left his megachurch in Michigan, moved to California and began appearing on Oprah Winfrey programs. Bell, at 48, has the number one spirituality podcast (RobCast) on iTunes, which is the measure today for what was once measured by people filling a stadium. Bell does not ask for conversions to Christianity per se, but challenges people to live authentic lives. His texts are not always Gospel-based or biblical, and his answers are complex.

All of which is to say: He is no Billy Graham.

This article appears in April 2 2018.

Jon M. Sweeney is a frequent contributor to America and the author of many books including Francis of Assisi in His Own Words and, for children, The Pope’s Cat series, illustrated by Roy DeLeon.