Activist groups have warned President Bush that if he nominates someone to the Supreme Court who is like his other judicial nominees, he will have trouble getting that candidate confirmed.

"Like Janice Rogers Brown (search), William Pryor (search), Priscilla Owen (search). He will be inviting a firestorm of opposition," said Nan Aron, president of the Alliance for Justice.

Owen, Brown and Pryor were confirmed to the federal bench as part of a deal hammered out in May by what is now known as the Gang of 14, seven senators from each party who agreed that a nominee would only face a filibuster, or procedural block, in "exceptional circumstances."

Click in the box to the right to watch a report by FOX News' Jim Angle.

No definition was given for what an exceptional circumstance would be, but Aron argues that anyone with a conservative philosophy like Owen, Brown and Pryor would easily qualify under that category.

"There is no question but that extraordinary circumstances would apply in that situation and there would be a filibuster," she said.

Supporters of the White House say the compromise under which those judges were confirmed set a clear definition of what is acceptable and what is not.

"It really takes off the table the ability of the left and the Democrats to argue on the basis of judicial philosophy that a nominee is not fit to serve on the Supreme Court," said Ben Ginsberg, head of Progress for America.

But some Democratic senators continue to warn darkly about trying to nominate an "unacceptable" nominee.

"If the president abuses his power and nominates someone who threatens to roll back the rights and freedoms of the American people, then the American people will insist that we oppose that nominee, and we intend to do so," said Sen. Ted Kennedy of Massachusetts.

Sen. Christopher Dodd, D-Conn., who has led the opposition to another Bush nominee, John Bolton, says that even with the Gang of 14 compromise, a filibuster is still an option.

"The 14 members who've spoken, I think there was an understanding [among them that] there would be reasonable nominees put forward," Dodd said.

Again, the definition of reasonable is in the mind of the beholder.

One member of the Gang of 14, Sen. Lindsay Graham, R-S.C., said the agreement to approve Owen, Pryor and Brown made clear that being conservative is no longer a justifiable reason to filibuster a nominee.

"The president has great leeway to pick a pro-life, strict constructionist, social and fiscal conservative to the court," Graham said, adding that if any member tries to filibuster the president's pick for the court, Graham would support the constitutional or "nuclear option," a process that would allow Republicans to vote along a party line with a simple majority to limit the use of filibusters for judicial nominees.

Sen. John Warner, R-Va., another member of the Gang of 14, said he hopes it won't come to that, but agrees that it's an option.

"The nuclear option is definitely on the table. We recognize that," he said.

With those two senators and others ready to fight, Republicans say they have enough support to change the rules to end judicial filibusters if Democrats threaten one.

That unity prompted one Republican official to say flatly that "no possibility" exists that opponents could deny an up-or-down vote on a Supreme Court nominee.

On Wednesday, supporters of the White House pointed to a report that Democratic Sen. Chuck Schumer of New York was overheard aboard a train telling someone on a cell phone call that some Democrats "are contemplating how we are going to go to war over this."

The phrasing led some to suggest that Schumer has decided to oppose any nominee, regardless of who is chosen.

But Schumer's spokesman said late Wednesday that Schumer has repeatedly said he hopes for a consensus nominee and the senator was only saying that if Bush nominates an extremist, Democrats "will not just roll over."