Political opportunity theory has proven extremely generative, highlighting the importance of macro-structural shifts in making established authorities vulnerable to insurgent challenge. But as critics point out, political opportunity theory flattens both culture and agency, and has fared poorly in explaining the timing of insurgency. Re-theorizing opportunity as leveraged by particular practices, rather than independently conferring to groups, redresses these limits, revealing the proximate causes of mobilization and influence. For a strategic test, this article revisits the forging ground of opportunity theory. Why did President Harry S. Truman, initially an apologist for the slow pace of racial reform in 1945–46, suddenly become an avid advocate of civil rights? Opportunity scholars argue that macro-structural forces caused Truman to advocate civil rights, generating the opportunity for insurgency by blacks as a group. But event structure analysis reveals how Black Anti-colonialist practices leveraged opportunities afforded by the earlier Progressive Challenge to compel Truman to adopt civil rights advocacy. Civil rights advocacy, in turn, allowed Truman to repress Black Anti-colonialist practices, even while setting the stage for the Civil Rights Movement to come. Different forms of insurgent practice leveraged opportunities created by different institutional cleavages; the same opportunities did not advantage all insurgency by a social group.