This essay examines the efforts of Upton Sinclair and Ernest Poole to connect their respective novels The Jungle and The Harbor to the nineteenth-century sentimental literary tradition, as well as their leftist allies’ reception of those efforts. Sinclair consistently presented The Jungle as a second Uncle Tom’s Cabin, capable of moving readers to agitate on behalf of working-class immigrants, while Poole engaged reflexively with the tropes and traditions of sentimentalism in order to model for his readers how they should respond to The Harbor. Although both novels became bestsellers and influenced later writers of proletarian fiction, early leftist critics dismissed Sinclair and Poole’s sentimentalism as aesthetically simplistic and politically naïve. This essay turns instead to a slightly later contemporary of those critics, Antonio Gramsci, whose prison writings argue for the revolutionary potential of sentimentalism. Reading The Jungle and The Harbor through the lens of Gramsci’s analysis of organic intellectuals and the cathartic power of popular literary forms, this essay contends, resolves many of the problems those early critics identified in the novels.