Stymied now on two of President Bush's judicial nominees, Republicans are considering an attempt to change Senate rules or suing to ban judicial filibusters, even against long odds.

"It certainly could be taken to court," Senate Majority Leader Bill Frist, R-Tenn., said after Democrats on Thursday successfully blocked Texas Judge Priscilla Owen from getting a federal appeals court seat.

The discussions reflect frustration among majority Republicans that Democrats have been able to sidestep Bush's popularity and undermine one of his platforms: putting more conservatives in key judgeships.

Bush called the Owen filibuster "shameful" and "unfair to this good woman and unfaithful to the Senate's own obligations."

"The Senate has a constitutional responsibility to exercise its advice and consent function and hold up or down votes on all judicial nominees within a reasonable time after nomination," he said in a statement.

Democrats are filibustering two nominees - Owen and Hispanic lawyer Miguel Estrada - and have promised more if divisive Bush nominees come to the Senate floor. It takes 60 votes to break a filibuster and Democrats showed Thursday with a 52-44 vote that they had a solid enough bloc to keep Owen off the bench. They say they will win again on Monday when Republicans try for the fifth time to force Estrada through.

"History will look kindly on us for doing so," said Sen. Charles Schumer, D-N.Y., "because never has a president of the United States been more ideological in his selection of judges."

The White House, GOP senators and advocates aides have been saying for months that they think filibustering judicial nominees is unconstitutional, but to test that theory someone would have to sue.

Republicans admit that they've thought about it. "One option that has been floated is the idea of a lawsuit," said Sen. John Cornyn, R-Texas on Wednesday.

Frist said he didn't know whether a lawsuit would be the right way to go.

"I can't predict whether that will be done or not, but ultimately I think the United States Senate will decide for itself" how to solve the problem, he told reporters.

Some observers say resorting to a lawsuit to ban filibusters would be futile.

"Even the thought that the courts would get involved in Senate business is mind-boggling," said Sheldon Goldman, a political science professor at the University of Massachusetts at Amherst who studies the federal appellate nomination process. "If this isn't a separation of powers issue, what is?"

Cornyn, a former Texas judge himself, agreed. "Another branch of the government - the judiciary - cannot come in and tell Congress how it must function."

Frist and other Republicans are also looking at changing the Senate rules to eliminate filibusters of judicial nominees.

Cornyn's Senate Judiciary subcommittee plans a whole hearing next week called "Judicial Nominations, Filibusters, and the Constitution: When a majority is denied its right to consent" to explore the issue and plans to change the nomination process.

"If filibusters are going to be made part of the judicial nominee process, I think you will see increasing discussion over whether the rules should be changed," Frist said.

The fact that the GOP's November takeover of the Senate has not made it any easier for Bush's appellate nominees to get confirmed only stokes Republican fury.

Democrats last year voted down Owen and Mississippi Judge Charles Pickering in committee and didn't hold hearings for others. The U.S. Appeals Courts are some of the most important courts in America, one step below the Supreme Court and deciding most of the nation's law.

Senate Judiciary Chairman Orrin Hatch, R-Utah - who is on the front line of the judicial battles - finally boiled over a Wednesday hearing. Schumer was strongly questioning appellate nominee John Roberts at his second hearing for his nomination for the U.S. Court of Appeals for the District of Columbia, when Hatch finally tired of the questions.

"Some I totally disagree with," Hatch said. "Some I think are dumb ... questions, between you and me. I am not kidding you. I mean, as much as I love and respect you, I just think that's true."