"As long as the administration continues to do this, we will continue to block judges who are outside the mainstream," Sen. Charles Schumer, D-N.Y. said.
Estrada's withdrawal Thursday from consideration for the U.S. Circuit Court of Appeals for the District of Columbia makes him the first high-profile Bush judicial nominee to ask that his name be removed from Senate deliberation.
Republicans failed on seven tries to get the 60 votes needed to break a Democratic filibuster on Estrada, never getting more than 55 votes in the 100-member Senate.
"Mr. Estrada received disgraceful treatment at the hands of 45 United States senators during the more than two years his nomination was pending," said Mr. Bush, who aggressively tried to get the Senate to approve Estrada early this year but had been silent on the issue in recent months.
Democrats said they wouldn't let Estrada have a confirmation vote until he answered more questions and the White House released memos Estrada wrote while working for the Justice Department.
"One of the lessons here – and there are many – is that judicial candidates for these types of very powerful positions have to be willing and able to share their legal philosophies in fairly significant detail with senators. Estrada failed or refused to do that, and that caused Democrats in the Senate to dig in," said CBS News Legal Analyst Andrew Cohen.
The battle over Estrada's nomination was the most intense since the Senate confirmation hearings for Clarence Thomas, who was nominated by Mr. Bush's father and became the Supreme Court's lone African American justice. In a Wall Street Journal editorial Friday, Thomas's wife Virginia blasted Democrats for their treatment of Estrada.
"We allowed the U.S. Senate to erect a 'glass ceiling' in our courts — you can do all the right things in America, but if you do not agree with Ted Kennedy and Hillary Clinton, you need not apply as a federal judge," she said. "This is the message that Democrats hope minorities, in particular, get from their victory as they succeeded in repelling a talented man, who happens to be Hispanic, from public service."
But Democrats planned to give even more Bush nominees the same treatment. The Senate so far has confirmed 146 of Mr. Bush's 196 U.S. district and appeals court nominees.
For Estrada, who at one point was rumored to be a possible Supreme Court nominee, the withdrawal ends a two-year waiting game in which his nomination never got beyond the Senate floor.
"I believe that the time has come to return my full attention to the practice of law and to regain the ability to make long-term plans for my family," he said in a letter to the president.
Estrada, 41, an attorney who never had served as a judge, wanted a seat on the D.C. Circuit, which currently is split evenly between Republican and Democratic appointees. The court decides important government cases involving separation of powers, the role of the federal government, the responsibilities of federal officials and the authority of federal agencies.
Democrats argued that Estrada and Mr. Bush's other blocked nominees were too conservative to serve on the court.
Similar to Estrada, Democrats already are filibustering two other nominees — Texas Supreme Court Justice Priscilla Owen and Alabama Attorney General William Pryor.
"We cannot sit back and let other judicial nominees like Priscilla Owen and Bill Pryor suffer the same fate as Miguel Estrada," Senate Judiciary Chairman Orrin Hatch, R-Utah, said.
Two others, U.S. District Judge Charles Pickering of Mississippi and California State Superior Court Judge Carolyn Kuhl, also are expected to be filibuster targets, although Republicans have yet to seek votes on either on the Senate floor.
The GOP-controlled Judiciary Committee will move Pickering to the Senate floor for confirmation before the end of the session, Hatch said Friday.
And Democrats have at least three other judicial nominees in their sights, including two heading for the D.C. Circuit.
Democrats already are closely watching California Supreme Court Justice Janice Rogers Brown and White House lawyer Brett Kavanaugh, both nominated to seats on the D.C. Circuit.
Brown has been opposed by the NAACP, and Democrats say the jurist, who is black, frequently rules against discrimination victims. Kavanaugh is an associate of former Independent Counsel Kenneth Starr, and Democrats say he is widely credited with developing the White House's conservative nomination strategy.
"Unfortunately, the White House's recent nominees to the D.C. Circuit appear to continue a disturbing pattern of nominating judges who are extreme," said Sen. Edward Kennedy, D-Mass. "Hopefully today the president will get the message that his current approach to nominations is not working."