Cette thèse aborde la relation entre le mormonisme et la société américaine, à travers une étude détaillée de matériaux médiatiques. Plus précisément, les stratégies de légitimation des groupes mormons et les stratégies de délégitimation utilisées par les détracteurs de ces groupes religieux marginaux sont analysées. Depuis la naissance du mormonisme, en terre américaine, ce courant a entretenu des relations tendues avec la culture mainstream. La thèse décrit tout d’abord l'évolution des rapports entre les mormons et la société américaine dominante, du 19e siècle à aujourd'hui, puis s’attarde à une analyse des productions médiatiques récentes mettant en scène des mormons monogames et polygames, avec une insistance particulière sur la série télévisée de fiction Big Love (HBO 2006-2011). Mais plus qu'une étude de cas à propos des tensions entre mormons et société américaine, la thèse nous informe sur les notions de déviance et de normalité et sur leur évolution temporelle, et offre une relecture de l’histoire du mormonisme à partir de son articulation avec la sphère médiatique. L'analyse permet de faire ressortir la manière dont le discours public influence la position des groupes minoritaires. La thèse met également en lumière les effets positifs de l'utilisation des médias de masse par les petits groupes sociaux ou religieux. En montrant comment un groupe religieux d’une période à l'autre de son existence se retrouve tour à tour stigmatisé, toléré et même parfois célébré, la thèse ouvre des perspectives pour l’analyse d’autres groupes minoritaires. Un modèle théorique, qui expose les stratégies de légitimation et de délégitimation publiques des différents groupes mormons, est central à la thèse. Il est issu d'un processus de théorisation ancrée. / This thesis addresses the relationship between Mormonism and American society, through a detailed analysis of media materials. Specifically, legitimation strategies, put forward by Mormons communities, and delegitimation strategies, used by opponents of these marginal religious groups, are considered. Since the inception of Mormonism, in the United States, this religious movement has maintained tense relationships with mainstream culture. First, this thesis describes the evolution of relationships between Mormons and mainstream society, from the 19th century to the present era, and then includes an analysis of recent media productions presenting Mormons, with an emphasis on the fiction TV series Big Love (HBO 2006-2011). More than a case study about tensions between Mormons and mainstream society, this thesis informs us about the notions of deviance and normality and their temporal evolution, and offers a reinterpretation of the history of Mormonism through its articulation with the media. The analysis sheds light on the way public discourse influences the position of minority groups, and on the positive effects of mass media use by small religious or social groups. By explaining how a religious group can, from one period of its existence to another, be stigmatised, tolerated and even sometimes celebrated, this thesis opens perspectives for the analysis of other minority groups. A theoretical model, exposing the legitimation and delegitimation strategies of Mormon groups, is central to the thesis. This model was derived from a grounded theory analysis.

In 1852, the leadership of the Church of Jesus Christ of Latter-day Saints made the pivotal decision to publicize the doctrine and practice of plural marriage—something they had worked to keep out of the public eye for years. This decision came in response to federal and social pressures. They quickly moved to announce and defend plural marriage among Church members as well as broader society, including those in the federal government. Orson Pratt was chosen by Brigham Young to be the face and the voice of the Church concerning plural marriage, both in Salt Lake City among members and in Washington D.C., where he preached sermons and published a periodical on the subject. This thesis a) demonstrates why Orson Pratt was the ideal candidate for such an undertaking; b) assesses the motivation for and context of the public unveiling and defense of plural marriage; c) analyzes Pratt’s rhetoric of the first public treatise on the subject given to a Latter-day Saint congregation at a special conference on 29 August 1852; and d) compares the rhetoric and reasoning between Pratt’s sermon to the Saints and his persuasive periodical written to the nation from Washington D.C. titled The Seer. Pratt’s rhetoric is incisive and carefully tailored to his audience. Important nuances in argumentation arise as he publishes the Seer and strives to convince his fellow citizens that plural marriage is right before God, improves society, and that the Saints should be allowed to practice polygamy as an expression of religious freedom. Orson Pratt ultimately fails to make a difference in the national opinion of plural marriage, but is successful in establishing a foundation of principles and reason that would be employed by the Saints to defend the practice of plural marriage for decades.