Elmer Gantry is the story of a young roughneck who abandons his early ambition to become a lawyer and embarks on a career in the ministry. The opening sentence of the novel, “Elmer Gantry was drunk”, introduces one of Lewis's least likeable protagonists. While an undergraduate in an obscure denominational college, Elmer discovers that he loves to be the center of attention. While he is drunk one day in a small town near the college, he is lead to defend a classmate who is preaching on a street corner. Elmer beats up an irreverent heckler and then says a few words in support of religion. From that point on, the classmate and members of the faculty identify Elmer as a candidate for the ministry and try to convert him. In spite of the fact that he is tempted by the social position the ministry would offer, Elmer resists because he does not feel “the call” to preach, but at a crucial point he is converted, more by the power of raw whiskey than by his faith. After graduation, he moves on to a Baptist seminary.
Elmer is ordained a Baptist minister and licensed to preach after two years in the seminary, but he fails to graduate when he is dismissed after seducing a young woman and going on a drunken spree. He channels his power of persuasion into a secular field, selling farm implements, but he misses the attention that he received as a preacher. His chance to return to preaching comes when he meets Sharon Falconer, a successful itinerant evangelist. Elmer serves as her manager and becomes her lover but loses both her and his position when her new tabernacle is destroyed by a fire which kills Sharon. After a brief period as a “New Thought” evangelist, Elmer becomes a Methodist minister. He marries wisely and moves up from a small congregation to one of the largest in Lewis's imaginary Midwestern city of Zenith. There he builds up a large following, first by instituting his “lively Sunday nights”, which consist mostly of secular entertainment, and then by crusading against all of his former favorite vices, especially drinking and prostitution. Elmer is nearly defeated by a husband and wife who entrap him in a compromising situation and then attempt to blackmail him, but he is saved by a clever lawyer and returns victorious to his congregation. He is last seen admiring the ankles of a choir singer who will undoubtedly be his next conquest.
Lewis had prepared carefully for the writing of Elmer Gantry. Years before he had encountered a Methodist minister named William Stidger who had encouraged him to write a novel about a clergyman. To do his research for Elmer Gantry Lewis moved to Kansas City, where Stidger was pastor, and began to invite local clergymen to his hotel suite for lively theological debates known locally as “Sinclair Lewis's Sunday School”. (Not usually a very religious man, Lewis had spent a brief period of his youth intensely interested in theology.) Among the clergymen he met, he found a kindred spirit in L. M. Birkhead, a Unitarian minister who acknowledged that he was an agnostic in spite of his calling. It was during his stay in Kansas City, during which Lewis often spoke from the pulpits of his new acquaintances, that Lewis was reported by the New York Times to have dared the Deity to strike him dead. The report was greatly oversimplified, but it served to awaken interest in Lewis's novel in progress.
Although Gantry's escapades are the most sensational feature of the novel, Lewis levels more mundane criticisms against the clergy through a host of secondary characters. Ministers are portrayed as too committed to the rituals and ceremonies of the church, as obsessed with money-raising, as backbiters who attack their rival clergymen as viciously as George Babbitt attacked rival realtors, as effeminate bumblers, and as men who are too sheltered from everyday life to respond to the needs of their congregations. The worst are toadies to the rich who scorn the very sinners that Christ sought to help. Perhaps the worst criticism emerges from the career of Frank Shallard, a divinity school classmate of Elmer's. Frank's career in the ministry reverses Elmer's. He is a hard-working student who sincerely attempts to follow the career path of his minister father, but he is tormented by doubts. He is pastor of a small, poor church in Zenith while Elmer is rising to prominence. Finally, moved by the hypocrisy of his fellows and his own doubts, he leaves the church to help people by working for a secular charity. For publicly speaking out against Fundamentalist bigotry in the wake of the Scopes Monkey Trial over the teaching of evolution, Frank is kidnapped and beaten so badly that he loses his eyesight and is permanently disabled.