IT’S PROBABLY UNCONSTITUTIONAL, TOO…. Arguments against Senate filibusters are no doubt familiar to you by now. They’re undemocratic; they make governing next to impossible; they breed cynicism; they undermine American competitiveness; etc.

What you may not have heard is the argument that requiring supermajorities to pass legislation through the Senate is arguably unconstitutional. Thomas Geoghegan makes a very compelling case in the New York Times, noting the ways in which the U.S. Constitution — which makes no reference to filibusters — is at odds with a system that allows 41 senators, representing just over 10% of the U.S. population, to “block bills dealing not just with health care but with global warming and hazards that threaten the whole planet.” The “routine use of supermajority voting is, at worst, unconstitutional and, at best, at odds with the founders’ intent.” (via Kevin Drum)

First, the Constitution explicitly requires supermajorities only in a few special cases: ratifying treaties and constitutional amendments, overriding presidential vetoes, expelling members and for impeachments. With so many lawyers among them, the founders knew and operated under the maxim “expressio unius est exclusio alterius” — the express mention of one thing excludes all others. But one need not leave it at a maxim. In the Federalist Papers, every time Alexander Hamilton or John Jay defends a particular supermajority rule, he does so at length and with an obvious sense of guilt over his departure from majority rule.

Second, Article I, Section 3, expressly says that the vice president as the presiding officer of the Senate should cast the deciding vote when senators are “equally divided.” The procedural filibuster does an end run around this constitutional requirement, which presumed that on the truly contested bills there would be ties. With supermajority voting, the Senate is never “equally divided” on the big, contested issues of our day, so that it is a rogue senator, and not the vice president, who casts the deciding vote. The procedural filibuster effectively disenfranchises the vice president. […]

Third, Article I pointedly mandates at least one rule of proceeding, namely, that a majority of senators (and House members, for that matter) will constitute a quorum. Article I, Section 5 states in part that “a majority of each shall constitute a majority to do business.” Of course, in requiring a simple majority for a quorum, the founders were concerned about no-shows for a host of reasons — not least of all because the first legislators had to travel great distances by stagecoach.

But the bigger reason for the rule was to keep a minority from walking out and thereby blocking a majority vote. In Federalist No. 75, Hamilton dismissed a supermajority rule for a quorum thus: “All provisions which require more than a majority of any body to its resolutions have a direct tendency to embarrass the operations of the government and an indirect one to subject the sense of the majority to that of the minority.”

It would be illogical for the Constitution to preclude a supermajority rule with respect to a quorum while allowing it on an ad hoc and more convenient basis any time a minority wanted to block a vote. Yet that is essentially what Senate Rule 22 achieves on any bill that used to require a majority vote.

Reads like a pretty tight case to me.

Of course, challenging the constitutionality of the oft-abused procedure is inherently tricky. Getting standing to file suit would be difficult, and the courts would be reluctant to consider a procedural matter from a co-equal branch of government.

But if there were a court case, Geoghegan’s argument would, I suspect, be quite persuasive.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.