Abstract: The U.S. Senate is an undemocratic institution in two respects. First, the filibuster rule allows a minority of Senators to block a final vote on most measures. Second, the Senate’s malapportionment means that a Senate majority often represents a minority of the population. Eliminating the filibuster would address the first problem but would exacerbate the second. Most proposals for addressing the Senate’s malapportionment either do so only indirectly and contingently, or would require unlikely changes to the Constitution or constitutional doctrine. We therefore propose that the Senate replace its current filibuster rule with what we refer to as a “popular-majoritarian cloture rule.” Under this rule, a motion to close debate and proceed to a final vote would carry if but only if supported by a majority coalition of Senators who collectively represent a larger share of the population than those Senators in opposition. This rule, which would be a constitutional exercise of the Senate’s power to set the rules of its proceedings, would make the body more democratic, legitimate, and functional, and would be prefer-able both to the current filibuster rule and to simple majority rule. The democratic illegitimacy and dysfunction of the U.S. Senate as it currently operates justifies the consideration of institutional reforms that might seem, at the moment, both extreme and unlikely. Repairing American governance requires fixing the Senate, and our proposal illustrates one way to democratize the Senate from within.