WASHINGTON -- The group of 14 senators who forged a last-minute compromise Monday evening to avoid a vote on abolishing filibusters of judicial nominations left key questions unanswered -- including exactly what the Democratic signatories meant when they promised to filibuster future nominees only in "extraordinary circumstances."

But the question that most intrigued senators, activists and journalists yesterday was how the agreement by the "Gang of 14" would shape the next nomination to the U.S. Supreme Court.

That a vacancy is likely sooner rather than later was dramatized by the visit to the U.S. Capitol Medical Department on Monday by 80-year-old Chief Justice William H. Rehnquist, who has been receiving treatment for thyroid cancer and who is widely expected to retire at the end of the court's term in June.

Senators, academics and activists debated yesterday whether the compromise would make it less likely that President Bush would name a provocative conservative to succeed Rehnquist -- such as Associate Justices Clarence Thomas or Antonin Scalia.

Sen. Trent Lott, R.-Miss., made a particularly combative prediction.

"We're going get a conservative man or woman on the Supreme Court in the next vacancy," Lott said. "Bush is going to nominate a conservative. Get over it, Schumer and Boxer," he said, referring to Democratic Sens. Charles Schumer of New York and Barbara Boxer of California.

Both of Pennsylvania's Republican senators suggested that Bush would have a freer hand in making Supreme Court appointments than before the compromise.

"There's play in the joints," Sen. Arlen Specter said at a morning news conference that was arranged before Monday night's compromise as a showcase for supporters of the Bush nominees.

Specter said the agreement, while less favorable to the president than the abolition of the filibuster would have been, returns relations between the president and Senate to what they were before 1987, when Senate Democrats defeated then-President Ronald Reagan's nomination of Robert H. Bork to the Supreme Court.

Sen. Rick Santorum told a separate news conference that "everyone feels strongly that there will be no filibuster of a Supreme Court nominee who is a qualified nominee."

But Eleanor Smeal, president of the Feminist Majority, said the compromise meant that "at least we have a chance. Without any possibility of a filibuster, we would have no chance under the present circumstances of blocking an extreme anti-women's rights and civil rights Supreme Court nominee."

Academic observers suggested that the compromise was a work in progress that could be tested by a controversial Supreme Court nominee.

"Although this deal gives President Bush some of what he wants, it doesn't strengthen his hand as much as abolishing the filibuster would have done," said Michael Comiskey, an associate professor of political science at Penn State University's Fayette campus and the author of "Seeking Justices: The Judging of Supreme Court Nominees."

Comiskey said the effect of the compromise on a future Supreme Court nomination will depend on how Democrats and Republicans interpret "extraordinary circumstances."

"That's the rub," Comiskey said, predicting that if Democrats filibustered in a situation that did not meet the Republicans' definition of "extraordinary," the majority party might revive the so-called nuclear option and abolish the filibuster for judicial nominations.

Paul Rosenzweig, senior legal research fellow at the Heritage Foundation Center for Legal & Judicial Studies, agreed that a lot will depend on the interpretation of "extraordinary circumstances."

"Here's the question I would have asked if I were a Republican in that room," Rosenzweig said. "Does the Democrats' agreement not to filibuster except in extraordinary circumstances mean that they won't filibuster someone for the Supreme Court who has already been confirmed for an appellate position? If that's the case, the Democrats have checked a significant weapon at the door."

Specter, the Senate Judiciary Committee chairman -- who had attended the talks leading to the compromise but was not among the 14 senators who signed it -- said the deal might even open the way for Bush to nominate to the Supreme Court an early casualty of the Democrats' filibuster strategy: former Justice Department lawyer Miguel Estrada. A Honduran immigrant who was widely discussed as a future Supreme Court justice early in Bush's first term, Estrada withdrew his nomination for a seat on the U.S. Court of Appeals for the District of Columbia Circuit in 2003 and is reported to be uninterested in another judicial nomination.

In a speech on the Senate floor, Sen. John Cornyn, R-Texas, who complained that the compromise "does not solve anything," devoted particular attention to Estrada, saying he had been the victim of character assassination. "I think about Miguel Estrada, who waited two years for an up-or-down vote with the wonderful American success story, but after two years he simply had to say: 'I can't wait any more. My reputation cannot sustain the continued unjustified attacks. I am simply going to withdraw,' " Cornyn said.

Specter said: "I've heard a lot of Democrats say they made a mistake in filibustering Estrada. Whether that's a ticket to the Supreme Court is another matter."