Controversy over the Senate’s filibuster practice dominates modern discussion of American legislative government. With increasing frequency, commentators have urged that the upper chamber’s requirement of sixty votes to close debate on pending matters violates a majority-rule- based norm of constitutional law. Proponents of this view, however, tend to gloss over a more basic question: Does the Constitution’s Rules of Proceedings Clause permit the houses of Congress to adopt internal parliamentary requirements under which a bill is deemed “passed” only if it receives supermajority support? This question is important. Indeed, the House already has such a rule in place, and any challenge to the Senate cloture rule is doomed from the start if that body may self-impose supermajority voting thresholds even for the actual enactment of laws. Existing scholarly work in this area, however, is incomplete. The most elaborate treatments invoke originalist principles to claim that the chambers of Congress may freely adopt supermajority (as well as submajority) bill- voting requirements. These treatments have spawned critical responses, but none of them focuses in full-blown fashion on the words and deeds of the Framers themselves. This Article fills the resulting gap by offering a wide- ranging argument against supermajority voting rules based on constitutional text, constitutional structure, and background understandings that pervaded the framing period. Taken as a whole, these controlling indicators of original meaning establish that a bill is passed if and only if it receives a majority vote.