Sounding a refrain common among President Bush's judicial nominees, Miguel Estrada promised a Senate committee Thursday that he would base his rulings on fact, not personal opinions, if he were to be confirmed as a federal appellate court judge.

"I'm very firmly of the view that although we all have views on a number of subjects from A to Z, the job of a judge is to subconsciously put that aside and look at each case," Estrada told the senators.

"I give you my level best solemn assurance that I think firmly that I do have those qualities, or I would not have accepted the nomination," said Estrada.

Estrada needs to convince at least one of 10 Democrats on the Senate Judiciary Committee that his support from conservative groups and legal work on behalf of Bush's election shouldn't bar him from sitting on the court.

Republican Sens. John Warner and George Allen, both of Virginia, praised Estrada's legal work as the hearing got under way Thursday.

"Miguel Estrada is truly a man of great character," Allen said. "He's everything we talked about, about opportunity and the American dream."

Added Warner: "This is an extraordinary example of achievement on the American scene. Everything that my colleagues and I and others have seen indicates that he is imminently qualified."

Democrats have complained that Estrada has no judicial experience and has a rigid ideological background.

"We know very little about who he is and what he stands for and how he comes to his positions," said Sen. Charles Schumer, D-N.Y., a leading opponent of placing conservatives on the federal bench.

Estrada's political views are not entirely clear.

Nominated for the District of Columbia Circuit Court of Appeals 16 months ago, Estrada has bewildered critics who fear that the naturalized Honduran would endanger civil rights.

"Miguel Estrada has a reputation for an extreme conservatism that gives rise to concerns that he will, if confirmed, roll back established rights and protections," said Marcia Kuntz of the Alliance for Justice.

But Estrada's opponents concede they can't prove that Estrada is staunchly conservative and therefore, in their opinion, unfit for the federal bench. Kuntz said, however, the burden is on Estrada to make the case.

His critics argue that the paper trail on Estrada's ideas about the law is thin, though he himself says that is not the case. Plenty of examples of his cases exist, including 15 cases that he argued before the U.S. Supreme Court. He won 10.

"I am not worried in the least that anybody could detect any bias or lack of skill in my legal work," he added.

Earlier this year, Senate Democrats asked the Justice Department to release briefs Estrada wrote during the five years he served as deputy solicitor general, but the Justice Department turned them down, saying that to do so would chill the candid exchange of legal opinions.

"Simply put, the department cannot function properly if our attorneys write these kinds of documents with one eye focused on the effect that their words, if made public, might have on their qualification for future office," Daniel J. Bryant, assistant attorney general, wrote to the committee in June.

One advantage Estrada may have going for him could be an unwillingness among Democrats to reject a Hispanic judicial candidate. If confirmed, he would not only be the highest-ranking Hispanic federal judge in the country, but also earn a place on Bush's shortlist for any Supreme Court vacancy.

"In this month in which we honor the achievement of Hispanic Americans, I can think of no greater or more meaningful gesture of honor than for the United States to confirm this person of ultimate qualification," Attorney General John Ashcroft said Wednesday during a Justice Department event commemorating National Hispanic Heritage Month.

Estrada, however, doesn't want to be a symbol for Hispanic achievement, judicial conservatism or Republican diversity. He would prefer to just stick to his story.

Born in Honduras, Estrada came to America at age 17 speaking serviceable English. He attended private high school and graduated with honors from Columbia University in New York. He then went to Harvard Law School, where he also graduated with honors while editing the law review.

He served for five years as deputy solicitor general in the Justice Department before entering private practice.

Bush on Wednesday called Estrada a "fine man" and an "excellent lawyer," and said he should be confirmed.

"The Senate should not play politics with this nomination for he will be an outstanding judge," the president said at a GOP Senate fund-raiser.

But Hispanic groups are split on the nomination. The Congressional Hispanic Caucus and the Mexican American Legal Defense and Educational Fund oppose Estrada. The U.S. Hispanic Chamber of Commerce, the Latino Coalition and the League of United Latin American Citizens all support him and have lobbied heavily for him over the past few months.

If Estrada is confirmed -- and Democrats have not yet set a date for a committee vote -- he will be the first judge confirmed for the D.C. appeals court in five years, and will fill one of four vacancies on the 12-member panel.

The court, considered one of the most important courts in America, decides cases that determine how federal agencies regulate topics like gas prices, clean air and water, labor practices and campaign finance reform.

It is currently split four-to-four between Republican and Democratic appointees.

If defeated, Estrada would be the third Bush nominee rejected this year -- three times the number rejected during the eight-year Clinton presidency.

Arguing that Bush's nominees are too partisan for the federal bench, Democrats already have rejected Bush nominees U.S. District Court Judge Charles Pickering of Mississippi and Texas Supreme Court Justice Priscilla Owen for the 5th Circuit Court.

Administration officials say that if Estrada fails to be confirmed, he will become a symbol for Democratic treatment of Bush judicial nominees.

"Unfortunately, the nominating process for judges has become increasingly partisan, and the president regrets that," said White House spokesman Ari Fleischer said Thursday. "Miguel Estrada is an outstanding nominee. The president strongly supports him and he hopes he will be passed."

Fox News' Major Garrett and the Associated Press contributed to this report.