Updated

The White House refused late Wednesday to release internal Justice Department memos written by one of President Bush's nominees to an important appeals court, setting up a partisan showdown over Miguel Estrada.

Democrats say they will use a filibuster to keep Estrada from being confirmed for the U.S. Court of Appeals for the District of Columbia Circuit until the Washington lawyer answers more of their questions. The party says it has the 41 votes necessary to maintain a filibuster.

Meanwhile, Fox News has learned that Senate Republicans are urging the White House to get more involved in the Estrada battle. Sources say one strong suggestion is for Bush to make a swing or two through the states of senators who are facing tough reelections — or other key states like Florida.

Democrats are demanding internal memos Estrada wrote while working at the Justice Department to get an idea of how Estrada would think as a judge.

But White House counsel Alberto Gonzales told senators in a letter Wednesday that the Bush administration would not release the documents and that Justice normally does not release such documents. All of the living former solicitors general, four Democrats and three Republicans, have agreed with the White House's position, he said.

"That is a fundamental principle that has been followed irrespective of the party that controls the White House and the Senate," Gonzales said.

Democrats said this means the debate will drag on. "I regret that the White House remains recalcitrant and continues to stand in the way of a solution to this impasse," said Sen. Patrick Leahy of Vermont, the top Democrat on the Judiciary Committee.

Despite the stalling tactics, several of Bush's picks for judicial positions are expected to be confirmed on Thursday.

Estrada supporters in the Senate are struggling to get out the word that Democrats are conducting the first-ever partisan filibuster of a judicial nominee.

Republicans say they do not want to vote to stop debate, lest they set a precedent and raise the bar on judges in the future. The GOP has the 51 votes needed to confirm Estrada, but refuses to say whether or not they have the required 60 votes to defeat a filibuster, arguing that "nobody knows how many votes they have until they are counted."

Bush said the Democratic blocking tactic was "shameful politics." Senate GOP leader Bill Frist warned Democrats that he might force them to stay in the Senate chamber at night and on weekends until he gets a final vote.

"I think it is important for America to understand that your side of the aisle is — whether or not you use the word filibuster or not — is obstructing or stalling a process that is important to our judicial system," said Frist, R-Tenn.

Democrats are looking for material they can use against Estrada, since he didn't provide them with anything controversial during his confirmation hearing last year, said Senate Judiciary Chairman Orrin Hatch, R-Utah. "They couldn't dig up any dirt on him," Hatch said. "So what are they doing now? Trying to see through a fishing expedition if they can find some documents where they can."

More than a dozen House Republicans, including Majority Leader Tom DeLay, came into the Senate chamber Wednesday night to hear GOP speeches backing Estrada. "They wanted to support the Senate," said DeLay, R-Texas.

A traditional filibuster - where lawmakers take over the floor and refuse to go home until they get their way — is rare today, Senate historian Don Ritchie said. "The old image of Mr. Smith Goes to Washington and one senator holding the Senate for hours and hours doesn't happen anymore," Ritchie said.

Senate leaders have decided it is more efficient to get unanimous consent to "freeze" the bill that is being filibustered in place and jump to another track and process a different bill on which there is less controversy. This keeps the legislative agenda moving forward while leaders negotiate the problematic bill behind the scenes.

Estrada backers say the war on terrorism has made it difficult for them to get their message out, and Democrats are getting away with a whisper filibuster that would set a precedent that could devastate the confirmation process not only for Bush but for presidents to come.

Democrats say Estrada lacks judicial experience and have complained about his refusal to answer questions about specific cases, including abortion rights, and to provide copies of the memos.

"It's simply not right for anyone to be asked to make a decision in the dark," said Senate Democratic leader Tom Daschle of South Dakota.

Since Estrada's nomination in May 2001, Republicans have accused Democrats of treating him unfairly because he is a conservative Hispanic.

Democrats "can vote against him. That is their right. And if that is what they want to do, that is the proper exercise of their constitutional duty," Hatch said.

"But to simply deny the Senate a vote is unfair to the nominee, it's unfair to this body, it's unfair to the president, it's unfair to the majority of senators who want to vote for this man."

Daschle said if they do not force Estrada to answer their questions, other Bush nominees will stonewall them. "If we don't draw the line here, we will never be able to draw this line," Daschle said.

Democratic aides say Democrats have 44 of their 48 senators agreeing to keep a filibuster going, with Sens. John Breaux of Louisiana, Zell Miller of Georgia and Ben Nelson of Nebraska against a filibuster and Sen. Blanche Lincoln of Arkansas on the fence.

And after two years of stalled judicial nominations, the Senate on Thursday expects to win committee approval for four of Bush's appellate court nominees.

Ohio lawyer Jeffrey Sutton, Ohio Supreme Court Justice Deborah Cook and Maryland lawyer John Roberts had been scheduled for confirmation hearings almost two years ago, before Sen. Jim Jeffords of Vermont defected from the GOP and threw Senate control to the Democrats.

Hatch has said he would use his one-vote advantage on the Judiciary Committee to push Bush's judicial nominees quickly to the full Senate.

All three had confirmation hearings on Jan. 29, but Democrats spent most of their time grilling Sutton about legal stands he has taken on behalf of his clients. Sutton defended a convicted killer who was executed Wednesday in Ohio.

Sutton has also been criticized for trying to weaken federal civil rights protections, including the Americans with Disabilities Act. Dozens of disabled people protested his nomination in the hallways of Congress.

Justice Department lawyer Jay Bybee of Nevada also was poised to win committee approval for a seat on the 9th Circuit Court of Appeals.

Fox News' Carl Cameron and The Associated Press contributed to this report.