How are political subjects made under conditions that continually delimit their political agency? This lecture theorizes youth organizing as a site of political formation, focusing on young Black organizers involved in the racial justice movements of the 2010s and the struggle to "Defund the Police." I argue that political agency is not a possession individuals bring to political life, but a capacity forged through collective struggle: through organizing, political education, dissent, and the experimental work of testing the boundaries of political possibility. Yet, I am ultimately concerned with the afterlife of movements: how political capacities persist, mutate, or disappear when mobilization ends, and what their uneven survival reveals about the structure through which Black political subjectivity is produced. Drawing on political theory and archival materials, I argue that political ontology is materially contingent: the capacities through which political subjects emerge, act, and persist depend upon the social, organizational, and material conditions that movements create and struggle to sustain.