Does deliberation produce any lasting effects? “America in One Room” was a national field experiment in which more than 500 randomly selected registered voters were brought from all over the country to deliberate on five major issues facing the country. A pre-post control group was also surveyed on the same questions after the weekend and about a year later. There were significant differences in voting intention and in actual voting behavior a year later among the deliberators compared to the control group. This article accounts for these differences by showing how deliberation stimulated a latent variable of political engagement. If deliberation has lasting effects on political engagement, then it provides a rationale for attempts to scale the deliberative process to much larger numbers. The article considers methods for doing so in the context of the broader debate about mini-publics, isolated spheres of deliberation situated within a largely non-deliberative society.