Mr. Dehlin was working for Microsoft and serving as a volunteer religious schoolteacher in 2001 when he said he first stumbled across “troubling and hard to find historical facts” about the church and its teachings in the Book of Mormon and other scriptures.

He says he founded the “Mormon Stories” podcast in 2005 to explore those issues with others, and has posted hundreds of lengthy interviews with Mormon scholars, historians and key figures in church culture. Many of the podcasts have been downloaded as many as 50,000 times, and others twice that amount.

Jana Riess, a Mormon columnist at Religion News Service, said that Mr. Dehlin’s interviews included a broad spectrum of Mormons, including the orthodox, the curious, the doubters and the heretics — and that his following was similarly diverse.

“The church is trying to work out what is acceptable discourse. Obviously, this is the 21st century and there are now tens of thousands of people who are online discussing Mormonism every day, and some of the public comments are not orthodox,” Ms. Riess said. “The question becomes, how can you police that, or do you even try? I think this is something they are still working out.”

Critics of Mr. Dehlin say he has been courting excommunication for years by publicly disavowing some Mormon teachings. But the role he has played in modern church affairs is far more complex. He founded a website, staylds.com, as a forum to persuade doubters to remain in the church. In recent years, he said, he was asked to share data he had collected with church officials on Mormons who wrestle with doubts and how to retain them in the church.

But Scott Gordon, president of FairMormon, a group that defends the church, said that the likely reason Mr. Dehlin was facing excommunication is that he is a nonbeliever who advocates nonbelief.

“He wants to belong to the culture, to the community, but he doesn’t believe in the faith,” Mr. Gordon said.

Each time Mr. Dehlin has been under investigation, he has submitted letters from hundreds of Mormons who testified that he persuaded them to remain in the church. Some ex-Mormons shun Mr. Dehlin’s website for that very reason: They say it is geared too much toward persuading people to stay in the faith.