The U.S. Senate has a venerable tradition of being more deliberative and less buffeted by populist winds than the House of Representatives. But since the war on terror began, the voices of conscience in the Senate have not been assertive enough in opposing the excesses of the Bush administration. To the great honor of the upper chamber, that was not the case last Wednesday.

In an action that restores some faith in American ideals, the Senate voted 90-9 in favor of an amendment to a military spending bill that would ban torture of prisoners in the custody of U.S. forces. Both of Pennsylvania's Republican senators, Rick Santorum and Arlen Specter, voted with the majority.

It is extraordinary that such a measure even had to debated, but the shaming incidents caught on film at Abu Ghraib prison in Iraq, in particular, underscore the need to uphold the moral legitimacy that the president always asserts and yet often fails to act upon. Unbelievably, the White House threatens to veto this measure if it survives in the conference committee that will try to iron out the differences in the House and Senate spending bills (the House measure contains no anti-torture language).

Two principled Republicans, Sens. John McCain of Arizona and Lindsey Graham of South Carolina, led the charge. As Sen. McCain, himself the victim of torture as a prisoner of war in North Vietnam, told the Senate, the amendment has two purposes: to make the Army Field Manual the uniform standard for the interrogation of detainees and to prohibit the cruel, inhumane and degrading treatment of prisoners.

This amendment is not about treating terrorists with kid gloves. It is about upholding the honor of American forces and clarifying what sort of a people we are as a nation.

Sen. McCain told his colleagues that he had received a letter from a captain in the 82nd Airborne -- a veteran of Iraq and Afghanistan -- who sought in vain to know the rules regarding the proper treatment of prisoners. The captain wrote: "I strongly urge you to do justice to your men and women in uniform. Give them clear standards of conduct that reflect the ideals they risk their lives for."

But it is not just some fuzzy idea of honor that animates this amendment. It is also practical. Torture elicits intelligence that can't be trusted. It frequently backfires and serves the ends of terrorists by blackening the reputation of the United States -- witness the Abu Ghraib fiasco. It also has the potential to rebound on American forces.

As Sen. Graham pointed out: "We take this moral high ground to make sure that if our people fall into enemy hands, we'll have the moral force to say, 'You have got to treat them right.' If you don't practice what you preach, nobody listens."

That argument is irrefutable, which is why more than two dozen former high-ranking military officers, including former Secretary of State Colin Powell, support the amendment. Their distinguished ranks are a reminder the United States does not have to stoop to abuse in order to defeat terrorism.