Earlier this month the liberal advocacy group Common Cause filed this case challenging the constitutionality of the Senate's filibuster rule. The lead attorney is Emmet Bondurant, author of this 2010 article on the subject. Ezra Klein has a sympathetic account in the Washington Post: Is the Filibuster Unconstitutional?:
At the core of Bondurant’s argument is a very simple claim: This isn’t what the Founders intended. The historical record is clear on that fact. The framers debated requiring a supermajority in Congress to pass anything. But they rejected that idea.
In Federalist 22, Alexander Hamilton savaged the idea of a supermajority Congress, writing that “its real operation is to embarrass the administration, to destroy the energy of government and to substitute the pleasure, caprice or artifices of an insignificant, turbulent or corrupt junta, to the regular deliberations and decisions of a respectable majority.”
In Federal 58, James Madison wasn’t much kinder to the concept. “In all cases where justice or the general good might require new laws to be passed, or active measures to be pursued, the fundamental principle of free government would be reversed. It would be no longer the majority that would rule; the power would be transferred to the minority.”
At Reason, Shikha Dalmia has amusingly caustic comments: The Misguided Anti-Filibuster Crusade of Progressives.
Ed Whelan at NRO Bench Memos has this legal assessment: Why Common Cause Is Wrong about Filibusters. The core of his analysis is:
The Constitution confers on each House of Congress the broad authority to “determine the Rules of its Proceedings.” (Art. I, § 5.) Each House exercises that authority by a majority of members present and constituting a quorum. (The Constitution states that “a Majority of each [House] shall constitute a Quorum.”) As I argued in one of my very first Bench Memos posts seven years ago, the authority of each House to “determine” its rules necessarily includes the authority to revise them at any time—again, by the same vote of a majority of members present and constituting a quorum.
In other words, I believe that any Senate rule that requires a supermajority vote may at any time be superseded or displaced by a majority of the Senate (not just by a majority vote of the entire Senate, but even by a majority of senators present and constituting a quorum—which majority could be as few as 26 senators). That’s why, for example, it was entirely proper for Senate Republicans in 2005 to seek to abolish, by majority vote, the practice of filibustering judicial nominees.
In sum, the Senate filibuster, far from being (as Common Cause contends) “inconsistent with the principle of majority rule,” continues to exist precisely because a majority of senators allows it to.
For some fun history, see this 2005 op-ed by John McGinnis and Mike Rappaport. As they describe, at that time Senate Majority Leader Bill Frist argued that the filibuster was unconstitutional (Bondurant's position); Senate Republicans sought to eliminate the judicial filibuster by majority vote; and Senate Democrats sought to filibuster the change to the filibuster rule. McGinnis and Rappaport conclude, like Ed Whelan, that the filibuster rule is constitutional but that the Constitution requires it to be changeable by majority vote:
[The] constitutionally correct view is that the Senate can choose to retain the filibuster rule, but that a majority must be able to change it. The Senate can thereby exercise its full constitutional authority to fashion rules of procedure but past majorities of the Senate cannot put current majorities in a procedural straitjacket.