Estrada, nominated for a seat on the U.S. Court of Appeals for the District of Columbia, has been waiting for three months for a confirmation vote. But Republicans fell eight votes short of the 60 votes they needed to confirm Estrada. The vote was 52-39.
Earlier, Ohio Supreme Court Justice Deborah Cook was confirmed quickly by the Senate on a 66-25 vote for the 6th U.S. Circuit Court of Appeals in Cincinnati, which handles appeals from Ohio, Kentucky, Tennessee and Michigan.
Democrats say they won't let Estrada have a confirmation vote until he answers more questions and the White House releases memos Estrada wrote while working for the Justice Department. Democrats say they fear that Estrada would be an extreme right-wing judge if placed on the court and want more information about him.
The five unsuccessful votes to end the filibuster would not "have been needed if the administration had simply cooperated with the Senate," said Sen. Patrick Leahy, D-Vt.
Republicans say Democrats are treating Estrada unfairly because he is a conservative Hispanic, and their filibusters are unconstitutionally keeping President Bush's judicial nominees off the federal appeals bench.
"This debate is about the raw politics that have been used against Miguel Estrada, the first Hispanic ever nominated to the U.S. Court of Appeals for the District of Columbia," said Senate Judiciary Chairman Orrin Hatch, R-Utah.
Estrada is one of two Bush judicial nominees being blocked by Democrats. Texas Judge Priscilla Owen also was filibustered by Democrats last week, who called her pro-business and anti-abortion.
Bush criticized senators who "continue to engage in obstructionist tactics" and repeated his call for an end to the logjam on Estrada, Owen and his other pending judicial nominees.
"Our justice system relies upon an independent court system and when there are vacancies, the American people suffer," Bush said.
Democrats say they opposed Cook but did not mount a filibuster against her. Republicans hold a 51-48 advantage in the Senate, with Sen. Jim Jeffords of Vermont the only independent.
"Her record is extreme, even in comparison with her Republican colleagues on the Ohio Supreme Court," said Sen. Edward Kennedy, D-Mass. "She consistently seems bent on narrowly construing laws intended to remedy violations of the rights of individuals."
Republicans said Cook is ready to serve on the U.S. Appeals Court, the regional courts that are one step below the U.S. Supreme Court and decide much of the nation's law.
"This is someone with great integrity, great honesty and someone who would make a fine federal judge," said Sen. Mike DeWine, R-Ohio.