This article traces the history of factionalism in policy making and advocacy for persons with serious mental illness from deinstitutionalization to the present. The authors draw on deliberative democratic theory to illustrate how factionalist advocacy causes advocates and policy makers to fail in their duties to represent and develop policy in support of people with serious mental illness. The authors discuss how this factionalism has bred distrust and undermined efforts to address the needs of people with serious mental illness. They propose the formation of a Public Mental Health Policy Commission, guided by principles of deliberative democracy, to overcome factionalism and to improve policy making to meet the needs of people with serious mental illness. The commission must include a diverse array of stakeholders, especially individuals with lived experience of serious mental illness.