Filibusters in the US Senate have become the parliamentary maneuver everyone loves to hate. The technique may be losing its luster, but is it unconstitutional? 

A federal court in Washington on Monday takes up a legal challenge to the Senate filibuster brought by four House Democrats and the political reform group Common Cause, which calls the procedure "an accident of history, not included in the Constitution and never contemplated by its drafters."

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At issue are Senate rules allowing discussion without time limit and requiring a vote of three-fifths of the members, or 60 senators, to end debate. That 60-vote super-majority, the lawsuit contends, is at odds with the Constitution, which specifies only a small number of circumstances in which more than a simple majority is required -- overriding a veto, impeaching the president, or expelling a member, for example.

Those rules, the lawsuit contends, "are unconstitutional because they are inconsistent with the principle of majority rule," replacing it with rule by the minority.         

The challengers claim that the filibuster has strayed from the purpose of protecting the right of the minority to debate the merits of a bill, dramatized by an exhausted Jimmy Stewart holding the floor in “Mr. Smith Goes to Washington.”  Instead, they claim, it is used today to prevent the majority from debating controversial bills.

"Actual or threatened filibusters have become so common that it is now virtually impossible as a practical matter for the majority in the Senate to pass a significant piece of legislation or to confirm many presidential nominees without 60 votes," argues Emmet Bondurant, the high-powered Georgia lawyer representing the challengers.

The lawsuit comes to court as some senators vow to change the rules to make filibusters harder to mount and to reduce the requirement for 60-vote majorities to transact important business.

The Senate's original rules did not allow for unlimited debate. They were changed in 1806, though the first filibuster was not attempted until 1841. Only in recent years has its use exploded, with 92 by April of 2010, triple the total in the 1950s and 60s.

As the Senate operates now, a super majority of 60 votes is required to pass anything even remotely controversial.

Lawyers for the Senate urge the court to throw the lawsuit out, as federal courts have done with three previous challenges to the filibuster.

"This suit asks the court do what no court has ever done -- inject the judicial branch into the Senate's internal deliberations and usurp the Senate's power to determine its own rules and procedures," the body’s lawyers say in their court filings.

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They also argue that the Constitution's speech or debate clause ("for any speech or debate in either house, [senators and representatives] shall not be questioned in any other place") bars the lawsuit, which is filed against Senate officials.  The Supreme Court, the Senate lawyers say, has ruled that the clause blocks lawsuits challenging the broad sphere of legislative activity.