The Founders wove the majoritarian default rule into the fabric of the Constitution. Whenever the document authorized a federal institution to make a certain decision using some principle other than simple majority rule, the exception was specified in the document itself. Several of the Constitution's provisions prescribing supermajorities make little sense unless we assume that majority rule was the self-evident default rule. Thus, Article I presupposed that each house would pass bills by majority vote—except when trying to override presidential vetoes, which would require a special supermajority. The supermajorities for constitutional amendments likewise were designed to be more demanding than the simple majorities for ordinary statutes, and the Senate supermajority for treaty ratification was meant to erect a higher bar than Senate agreement to ordinary legislation (a higher bar meant to offset the absence of the House in the formal treaty-making process). Similarly, the exceptional supermajority rule that applied when a chamber sought to expel properly elected and eligible members is distinct from the simple majority required to exclude improperly elected or constitutionally ineligible candidates.
In an effort to parry this basic argument, some scholars have asked why if majority rule truly went without saying, the framers felt the need to specify, as they did in Article I, that a majority of each house would constitute a quorum. The obvious answer is that state constitutions and British practice varied widely on the quorum question, and thus there was no obvious default rule from universal usage.
The same basic majority-rule principle has always governed the House of Representatives and the Supreme Court. Five votes trump four on the high court, and in the House, 218 beats 217. There is nothing in the Constitution that suggests the Senate is any different. And throughout the Founding era the Senate practiced and preached majority rule. Senate history prior to the 1830s offers no notable examples of organized and obstructionist filibustering—and absolutely nothing like a pattern of systematic, self-perpetuating, entrenched frustration of Senate-majority rule. As Jefferson wrote as vice president and the Senate's presiding officer: "No one is to speak impertinently or beside the question, superfluously or tediously. … The voice of the majority decides."
Even as Senate minorities began to develop stalling tactics by mid-19th century, they typically did so with the indulgence of the Senate majority. Long-winded speechifying occasionally delayed the Senate's business without preventing majorities from ending debate at some point and taking a vote. The Senate was smaller and had less business to transact in those days, and it often indulged individual senators as a matter of courtesy. In turn, the indulged senators did not routinely try to press their privileges so as to prevent Senate majorities from governing. According to one expert treatise, before the 1880s "almost every obstructed measure was eventually passed despite filibustering opposition."
Only in the late 20th and early 21st centuries has the filibuster metastasized into a rule requiring a 60-vote supermajority for every important piece of Senate business. Over the years, the Senate has flirted with getting rid of Rule 22, the root of the trouble, but never pulled it off. Perhaps the most noteworthy attempt occurred in 1975, when a majority of the Senate upheld a constitutional ruling of the vice president—sitting in the presiding chair—that a simple majority could end debate on filibuster reform and scrap the old rule. Shortly thereafter, however, the Senate voted to reconsider its earlier action. In 2005, Republican senators frustrated by the success of the Democratic minority in blocking votes on various judicial nominations loudly threatened to revise the old filibuster rule by a simple majority vote—the so-called "nuclear option." But this never came to a conclusive floor vote. Instead, Democrats moderated their obstructionism and Republicans stowed their nukes.
So where does all this leave us today? Here is one clean way of pulling together the basic argument: It is obvious that the Senate must use some specific voting rule for setting its own rules for proceeding—a rule for how to vote on how to vote. If majority rule is not that implicit rule, what is? Especially since that is the rule the Senate used at the start, in 1789. Just as the first House and the first Senate each used majority rule to decide its procedures, every subsequent House and Senate may and must do the same, for nothing in the Constitution made the Congress of 1789 king over later Congresses. Our founding document makes all Congresses equal in this respect.
In fact, neither house has ever formally prescribed a supermajority rule for formal amendment of its rules. Not even Senate Rule 22 has the audacity to openly assert that it cannot be repealed by simple majority vote. Rather, the filibuster rule says that debate on its own repeal cannot be ended this way. If Rule 22 simply means that it should not be repealed without a fair opportunity to debate the repeal, then it is fully valid. But insofar as Rule 22 allows repeal opponents to stall interminably so as to prevent a majoritarian vote from ever being held, then Rule 22 unconstitutionally entrenches supermajority rule. It's a question for each senator to decide for him- or herself—and then to act on, by simple majority rule, just as the framers intended.
Correction, Jan. 7, 2011: This article originally stated that Rule 22 required the agreement of 60 senators to end debate. It requires a supermajority. (Return to the corrected sentence.)