We identify and analyze an enigma of U.S. Senate procedure. Why does its pivotal voter under simple-majority voting prefer that the body makes law using super-majority cloture (e.g., the filibuster, or threat thereof, within the strictures of Rule XXII)? Using a two-stage game of procedural choice and policy choice, we reveal and rationalize the Manchin Paradox and explore its implications for super-majoritarianism and legislative organization.