For three hours after the Senate takes up its business each day, Senate Rule XIX requires that “all debate shall be germane and confined to the specific question then pending before the Senate.” The rule was proposed by Senator John Pastore of Rhode Island and adopted “by a 57-25 vote on January 23, 1964.”
It is “customarily enforced only by a call to order from the floor.” “Any Senator may request unanimous consent to speak out of order on a nongermane subject.” The Congressional Research Service adds: “In practice, the Pastore rule rarely affects what Senators speak about on the floor.”