WASHINGTON, Nov. 11 - Democrats who had voted previously to prohibit abusive treatment of detainees in American custody provided the margin of victory on Thursday for a Republican-backed measure that would deny prisoners at Guantánamo Bay, Cuba, the right to challenge their detention in federal courts.

Four of the five Democrats who supported the provision to strip detainees at Guantánamo of the legal tool the Supreme Court gave them to appeal their incarcerations said on Friday that they drew the line at allowing the prisoners unfettered access to United States courts to challenge the underlying rationale for their detention. The Senate approved the measure, an amendment to a military budget bill, 49 to 42.

"A foreign national who is captured and determined to be an enemy combatant in the world war on terrorism has no more right to a habeas corpus appeal to our courts than did a captured soldier of the Axis powers during World War II," Senator Joseph I. Lieberman, Democrat of Connecticut, said in a statement.

Senator Kent Conrad, Democrat of North Dakota, said in a telephone interview that retired soldiers told him at a Veterans Day lunch in Fargo on Friday that they supported Senator John McCain's proposed ban on cruel and degrading treatment of prisoners but opposed giving detainees at Guantánamo Bay broader leeway to United States courts.

"I don't think giving enemy combatants access to the federal court system is a precedent we want to set," Mr. Conrad said.

Spokesmen for two other Senate Democrats who voted for the measure, Mary L. Landrieu of Louisiana and Ben Nelson of Nebraska, made similar statements. "He thinks they should stay in the military tribunal system, and if that system is broken, we should fix it, not move them out of it," said David DiMartino, a spokesman for Senator Nelson.

The vote on the measure, written by Senator Lindsey Graham, Republican of South Carolina, opened a window this week into the complicated Capitol Hill politics of setting the rules and procedures for how the nation treats detainees and adjudicates their grievances in the global war on terror.

The vote also came at a time when the White House and Mr. McCain are locked in tense negotiations over the language of his provision, which has twice passed the Senate in recent days and is now a critical sticking point in the House-Senate conference committee deciding the fate of a $445 billion military spending bill.

Senate Democrats led by Jeff Bingaman of New Mexico are gearing up over the weekend to launch a counteroffensive early next week to strike or at least soften the part of Mr. Graham's measure that bars Guantánamo prisoners from challenging their incarceration by petitioning in civilian court for a writ of habeas corpus.

Mr. McCain issued a statement Friday explaining his vote in support of Mr. Graham's amendment as a way to rid federal courts of petitions from prisoners on everything from the delivery of mail to the type of food allowed. But he also hinted that he might support a compromise next week.

"Based on ongoing discussions, it is entirely possible that the current version of the amendment will be modified to address concerns about lawful treatment and the scope of independent appeals," Mr. McCain said.

Josh Kardon, chief of staff to Senator Ron Wyden of Oregon, the fifth Democrat to vote for Mr. Graham's measure, suggested that Mr. Wyden was also looking for a compromise to make the Guantánamo tribunal process more accountable to the Senate and "ensure the fair and humane treatment of detainees."

Yet the prospects of eliminating or modifying Mr. Graham's measure are problematic. Seven of the nine senators who were absent for Thursday's vote are Republicans who will probably back his original version next week.

The two moderate Republicans from Maine, Olympia J. Snowe and Susan Collins, who voted for Mr. Graham's measure, both indicated strong support Friday for preserving the provision as is, although aides said no final decisions would be made until senators saw details of Mr. Bingaman's proposal.

"Senator Graham's amendment complements Senator McCain's amendment," Ms. Collins said in a statement. "At the same time, his amendment prevents detainees who are not U.S. citizens from filing habeas corpus lawsuits in federal courts."

Antonia Ferrier, a spokeswoman for Ms. Snowe, characterized her boss's concerns this way: "Do we need all those lawyers going down there to hear their complaints? It seems a little extreme to her. After all, we're talking about enemy combatants."

If approved in its current form by both the Senate and the House, which has not yet considered it but where approval is considered likely, the measure would nullify a June 2004 Supreme Court opinion that detainees had a right to challenge their detentions in court. Nearly 200 such petitions have been filed so far and are working their way through the federal court system.

A group of legal scholars, including Judith Resnick of Yale Law School, David Shapiro and Frank Michelman of Harvard Law School, and Burt Neuborne of New York University Law School, were circulating a letter on Friday urging senators to reject Mr. Graham's measure.

"The Graham amendment embodies an effort to alter fundamental precepts of our constitutional order," the letter said. "It consigns the protection of fundamental human liberties to unilateral executive determination."

As the debate intensifies next week over the Graham measure, a confrontation will also be brewing over Mr. McCain's provision. Vice President Dick Cheney asked Senate Republicans at their weekly private luncheon last week for the Central Intelligence Agency to be granted an exemption that would allow it extra latitude, subject to presidential authorization, in interrogating high-level terrorists abroad who might have knowledge about future attacks. That effort went nowhere.

This week, while Mr. Cheney was pheasant hunting with friends in South Dakota, President Bush's national security adviser, Stephen J. Hadley, opened negotiations with Mr. McCain, which so far have failed to break the impasse.

Commentary:
The Constitution isn't safe with these five democrats in office. They should be impeached or voted out of office. Conrad is good on budget issues and I let his abuses slip because he's so good on this ONE issue, but when it comes to violating the core of the constitution, that's too much.