It is now a truism of American politics that voters in White, postindustrial communities across the American Heartland favor the Republican Party, while those in multiracial, urban enclaves prefer the Democrats. Becoming Partisans: How Place Makes Politics in the American Heartland argues that this reddening of the Heartland has emerged through place-based processes, as voters make sense of postindustrial decline and national party politics from within their local communities. It shows how these place-based experiences help voters form and maintain the partisan attachments that are so consequential to American electoral outcomes. Becoming Partisans develops these arguments through a longitudinal, comparative ethnography of Iverson, Meriville, and Williston. All three are predominantly White, blue-collar communities in the Midwest, the very kinds of places that have been at the center of national debates about the rise of Republicanism in the American Heartland since the 1960s. And yet, they have voted differently for decades: Iverson is a Democratic county; Meriville is a Republican county; and Williston is a former swing county that has recently turned to the right. Based on eighteen months of fieldwork during the 2020 presidential election and the onset of the COVID-19 pandemic, I argue that local organizations—particularly the political activism of unions in Iverson and the civic engagement of churches in Meriville—help sustain a working-class Democratic community on the one hand and a Christian, Republican community on the other. But in Williston, where both kinds of organizations struggle to fulfill the community roles they once did, residents’ anger and fear over the death of their small town is increasingly captured in the populist rhetoric of the Republican Party. Together, these cases suggest a revision to our understanding of entrenched Republicanism in the American Heartland: I show that the same kinds of people do not necessarily react to changing party politics and economic dislocation in the same way, but rather, they interpret social and political dynamics from within their communities. This also means that the rise of right-wing populism among Whites facing status and economic threat is not a necessary product of deindustrialization or an increasingly multiracial society; rather, it is produced through an uneven, unsteady process that can be halted, or even reversed, at the most local levels.