Legislative battles sometimes produce unlikely victims. After clashing with Republicans for months, Democrats appear poised to win a major partisan victory on health care.

Yet while triumph could be imminent, some liberal lawmakers and pundits want another scalp.  Get rid of the Senate filibuster, they say. It’s an outmoded procedure that allows a minority of 41 votes to stop legislation. Like the spittoon and the handlebar mustache, it’s just another anachronistic piece of congressional history.  These “reformers” say the Senate should operate more like the House, where a simple majority regularly does whatever it pleases.

But here’s an inconvenient truth. The Senate wasn’t designed to operate like a smaller version of the House. And changing the filibuster rules would be a major mistake, not only resulting in more ideologically extreme legislation, but also changing the very purpose of the upper body in our constitutional system.

Columnist Ezra Klein in a recent Washington Post column argues the case for ditching the 60-vote threshold.  He believes the spike in congressional partisanship over the past generation justifies killing the filibuster.

“The modern Senate is a radically different institution than the Senate of the 1960s,” Klein writes, “… and the dysfunction exhibited in its debate over health care … has convinced many, both inside and outside the chamber, that it needs to be fixed.”

Klein’s views are understandable.  He wants Democrats to enact a progressive agenda.  Indeed, a review of Senate history reveals calls for filibuster reform appear regularly when the majority doesn’t get its way immediately.

Jay Cost, writing at Real Clear Politics last week, however, provides a superb counterpoint to those who want to deep-six the filibuster.  Even though the amount of “extended debate” has increased dramatically in the past several decades, he argues, the Senate process itself remains largely the same. What Cost doesn’t mention is the Senate already has changed its rules several times in the past three decades, making it easier to break legislative filibusters: the filibuster threshold was lowered from two-thirds (67 votes) to three-fifths (60 votes) in 1975, and the Senate made further modifications to avoid process delays in 1979 and 1986.

Yet Cost’s main point remains on target: the changed ideological makeup of Congress over the past half century is a good reason to keep the filibuster, not a justification to change the rules again.  Analyzing the Senate from 1965-2009, Cost finds that: 1. Democrats are now more uniformly liberal and Republicans more uniformly conservative; 2. The “extremes” in each party are farther apart than ever; and, 3. There is less overlap on the ideological spectrum (in the past, some Democrats were more conservative than some Republicans and some Republicans more liberal than some Democrats).

But rather than justify gutting the filibuster further, these transformations offer reasons to keep it. Here’s Cost’s argument:  Ending debate under today’s rules means the 60th Senator (as opposed to the 50th) becomes pivotal. Without his or her assent, the majority cannot invoke cloture (stop a filibuster) and the legislative proposal will die.  The 60th Senator is likely more “moderate” than the 50th (because Democrats also control the White House, without a filibuster they could pass legislation even with a 50-50 tie as Vice President Biden could cast a tie-breaking vote).  With a 60-vote threshold, Democrats have to modify legislation to win support from the most “moderate” elements of their caucus (think, for example, of Ben Nelson of Nebraska or Blanche Lincoln of Arkansas).  But if Democrats only need 50 votes, they don’t need the votes of these more moderate Senators, and the final bill would likely tilt more extreme.

Cost argues this phenomenon would occur irrespective of which party was in control.  A Republican majority that only needed to accommodate 50 Senators would pass more extreme legislation than a GOP majority required to find consensus among 60.
The House’s track record this year on cap and trade, health care, and other measures that required substantial modification to pass the Senate supports Cost’s thesis.

The filibuster was neither contemplated by the U.S. Constitution nor written into the original rules of the Senate.  It’s a practice that has evolved over time.  But the Framers envisioned the upper body as an institution that would operate differently than the House–the “saucer to cool the House’s legislative coffee,” as Thomas Jefferson famously observed.

Bicameralism is one of the key checks on excessive government power. Allowing the Senate to operate like a mini-House might help Democrats extend the reach of the federal Leviathan more broadly and efficiently in 2010. So it’s no surprise that those who support an activist, bigger government agenda want to change the rules to achieve those ends. But it would also violate a key tenet of our system’s genius and appear a lot less attractive to liberals if the political tides shift.

Gary Andres is vice chairman of research at Dutko Worldwide in Washington, D.C., and a regular contributor to THE WEEKLY STANDARD Online.