Republican Senate leader Bill Frist has proposed the so-called nuclear option: eliminating the filibuster, by which a minority of senators can stall a vote on a judicial nomination until 60 senators agree to stop debate.
Both sides invoke the Founding Fathers in their defense.
Frist and his allies say the Founders intended that the Senate decide on "advice and consent" via majority vote, while Democrats say that the rights of the minority are integral to our system of checks and balances.
What has been overlooked in this controversy is that the filibuster actually protects the majority -- of voters.
The current 100 senators were elected in 2000, 2002, or 2004. In those elections, more than 200 million votes were cast, out of which Republican candidates obtained 46.8 percent. That's right, not even close to a majority. The Democrats obtained 48.4 percent. Also not a majority, but more than the Republicans' votes.
In the 2004 Senate races, more than 50 percent of votes were cast for Democratic candidates, yet Republicans won 19 of the 34 seats at stake.
What about the Republican "landslide" of 2002? The party won 22 of 34 seats up that year -- a large majority, yet they did so on only 49.9 percent of the votes.
Only in 2000 did Democrats win most of the seats at stake, in an election in which the parties' votes were essentially tied (47 percent). Despite these Democratic pluralities of Senate votes cast since 2000, Republicans have 55 senators, and Democrats 44. The nearly 5 percent of voters who voted for independent or third-party candidates have no representation at all, as the only independent, James Jeffords of Vermont, was elected as a Republican in 2000. (He later defected from his party.)
It may be objected that this consideration of the partisan breakdown of votes ignores the fact that the Senate is not intended to be a partisan institution. It was, after all, established by the Founders to represent the states. That is precisely the issue at stake.
Should a partisan majority of senators be able to rule unchecked over an institution designed to give voice to all the states? Partisan majorities and state representation are contradictory principles. As a result, empowering the majority party undermines the purpose of the Senate. Critics of the filibuster note that the Senate would run more efficiently if the minority could not obstruct the chamber's business.
But which majority should rule free from obstruction -- that of senators themselves, or the voters they represent? If we want to allow a majority of Senators to speak for all the states, then we need to find a way to reconcile our new era of deepening partisan divisions with the immutable Constitutional principle of equal representation of the states.
When the Founders agreed that the Senate would have two members from each state, the ratio of largest to smallest state was 12:1. Today it is 70:1. This massive gap in state populations, coupled with increasingly polarized party lines that cut across state boundaries, are what give Senate elections a bias toward one party.
As seen in Senate elections since 2000, that bias clearly favors Republicans. Is there a way to reconcile the contradictory principles of partisan and state representation? Not with two senators per state, elected one at a time.
But if a state's senators were elected at the same time, and by a method that guarantees minority representation, the partisan bias would be diminished. It would work better still if each state's delegation were expanded to three senators.
Reforming the Senate to empower the majority is a fine debate to have. But so far the debate has been narrowly cast as a question of the majority of senators, and the voters have been neglected.
In the meantime, the filibuster may be imperfect. It may even from time to time obstruct the business of legislating and approving the president's nominations. But it is the best tool we have for ensuring that the majority of voters is not ignored by an unrepresentative majority of senators.
Matthew Soberg Shugart is professor of political science at the Graduate School of International Relations and Pacific Studies, at the University of California-San Diego.