This essay explores how contemporary political life is framed through engagements with material forms. Extending work that has demonstrated that politics is best understood not as a discursive or institutional sphere but as the effect of material engagements, the essay asks, just how is it that materials become the grounds for politics? Focusing on the history of a road construction project in the Peruvian Amazon, the essay illustrates how politics becomes realized through engagements that entail the affective force of emergent materialities that break through or rupture a normalized understanding of sociomaterial relations. This rupture cracks open a space for material diagnostics, wherein both familiar and unfamiliar political forms are able to take shape. Thus in material diagnostics are found both the potential for ontological difference and considerable repair work wherein the grounds for a future politics is remade.