That is precisely what Dobson claims Trump has done. Evangelicals have distinctive ideas about what constitutes religious conversion, which they call being “born again.” To be born again, one must make a decision to pray, repent sins, and accept Jesus’s salvation. Most evangelicals look to such a conversion as the decisive mark of whether someone is Christian or not; some regard Roman Catholics and mainline Protestants who have not been through this experience as not really Christian. Being born again is a matter of the heart rather than intellectual assent or institutional affiliation. Being born again can happen instantly, much like the biblical conversion of Saul of Tarsus on the road to Damascus. And just as Saul was an enemy of the church who became Paul the Apostle after his conversion, evangelicals believe the new birth can utterly transform anyone.

The evangelical idea of conversion has a long history in America, and that history shows why evangelicals care whether Trump has been born again. While the term “born again” comes from the Bible, the idea of new birth came to prominence during the colonial revivals of the 1730s and 1740s. Ministers like Jonathan Edwards, George Whitefield, and Gilbert Tennent preached the need for the new birth and “heart religion” as opposed to mere “formal” Christianity. These awakenings were the beginning of the movement that became evangelicalism in the United States and the rest of the English-speaking world.

The evangelical revivals of the 1830s and 1840s continued to develop the idea of conversion as new birth. The lawyer-turned-revivalist Charles Grandison Finney preached that sinners could exercise their wills and be converted instantly by praying to God. Religious publishers such as the American Tract Society published an enormous number of tracts spreading that message. These brief pamphlets were distributed to non-Christians to encourage them to convert to Christianity and show them how to do so. Drawing on biblical models, the ATS gradually learned to end its tracts with a brief “sinner’s prayer.” The potential convert was instructed to repeat this prayer as the decisive act by which he or she became a Christian.

Over the 19th century and into the 20th, evangelicalism moved into mainstream American religious and cultural life. While today’s conservative Christians often claim the United States was founded as a Christian nation, in fact, it took a great deal of missionary effort to evangelize the United States during the 19th century. And wherever home missionaries, Sunday school teachers, tract publishers, and revivalist preachers pressed the evangelical gospel, they brought the idea of conversion as new birth through a sinner’s prayer.

By the 1950s, evangelicals had routinized and institutionalized this process. The young evangelist Billy Graham preached to tens of millions of Americans over the following six decades. His sermons taught people how to be converted, then called them forward to pray and receive Christ. In 1952, the evangelist Bill Bright wrote a tract that he called “The Four Spiritual Laws.” It ended with a sinner’s prayer and promised “you can receive Christ right now by faith through prayer.” According to the organization Bright founded, at least one billion copies of that piece of writing have been distributed worldwide.