In keeping with the demands of political philosophers, America's constitutional design harnesses elected officials to the mass public's prevailing views, but also provides avenues for the opinions of disenfranchised groups and numerical minorities to be reflected in policy. We seek to shed light on this constitutional balancing act by studying U.S. senators’ decisions on thirty-six roll call votes related to the practice of slavery between 1835 and 1847. These voting decisions are modeled using the prevalence of antislavery petitions sent to Congress over the same period from each state's residents. We observe considerable and systematic senator representation of perceived majority opinion on antislavery petitions, despite the presence of nineteenth-century institutions buffering senators from the public. We also report evidence that the representation of disenfranchised women's views (as expressed in petitions) relative to those of men varied by party, and in ways that are predictable. Finally, we observe that senators sometimes represented perceived minority viewpoints, seemingly motivated by their political ambitions. These findings not only hold important implications for our understanding of democratic representation, but also for the processes of American political development.