WASHINGTON - Goodwin Liu couldn't speak English until kindergarten, but he went on to become his high school's co-valedictorian, then a Rhodes Scholar and a law professor at the University of California, Berkeley.

Now he is under attack on Capitol Hill, where Republicans are opposing his nomination to the U.S. Court of Appeals for the Ninth Circuit in San Francisco.

Liu, 39, the son of Taiwanese immigrants, is attracting far more attention than most judicial nominees. While his backers are excited by his solidly liberal credentials, some of his opponents fear that President Obama is preparing Liu, down the road, for what would be a historic appointment: the first Asian American on the Supreme Court.

"He's by far the most controversial nominee that Obama has named, and he's clearly being groomed for the Supreme Court, so there's every reason to give him a full dose of scrutiny," said Curt Levey, executive director of the conservative Committee for Justice. "Look, he was picked because he's a darling of the left, and that's exactly the reason conservatives are up in arms about him."

Liu, now the associate dean of the Berkeley law school, faces a difficult confirmation fight as the Senate Judiciary Committee prepares to take up his nomination. A hearing is set for Friday.

Liu has advocated many liberal causes, supporting national health care, affirmative action, same-sex marriage, and slavery reparations.

He angered conservatives by testifying against the confirmation of Supreme Court Justice Samuel A. Alito Jr. He has alarmed opponents by arguing that the Constitution should be interpreted based on "the evolving norms and traditions of our society," which conservatives call code for judicial activism. His opposition to the death penalty drew fire from 42 of California's district attorneys, who sent a letter to the Senate Judiciary Committee urging Liu's rejection.

Liu's record isn't universally liberal: He has backed charter schools and private school vouchers, which teachers unions oppose. He has drawn praise from conservatives such as Kenneth Starr, the lawyer who investigated President Bill Clinton, and California GOP Senate candidate Tom Campbell.

California's current senators, both Democrats, enthusiastically support Liu. Barbara Boxer called him an "inspired choice"; Dianne Feinstein said he was "as sharp as they come, with a kind demeanor and a good temperament."

Republicans are ready to make things tough for Liu.

While promising to withhold final judgment on the nominee, Sen. Jeff Sessions (R., Ala.), the top Republican on the Judiciary Committee, said Liu was a former board member of the American Civil Liberties Union who was "far outside the mainstream of American jurisprudence."

"It seems to me that his judicial philosophy does not respect the American ideal of judges as neutral arbiters of the law," Sessions said. "I hope my initial impressions are wrong."

Liu is refusing all media interviews before his confirmation hearing. He has plenty of supporters willing to speak for him, however.

Edwin Prather, president of the Asian Pacific Bar of California, said GOP senators shouldn't be challenging Liu, calling him a well-respected and highly qualified nominee.

"We need an Asian American on the Ninth Circuit bench," he said. "We need Goodwin Liu on that bench."

Vincent Eng, deputy director of the Asian-American Justice Center in Washington, called Liu "a very exciting nominee" with exceptional qualifications.

Liu, the child of two physicians, was born in Georgia and moved to Sacramento, Calif., when he was 7. He served as a page in the U.S. House, which sparked an interest in law and politics, and he has degrees from Stanford University and Yale Law School.

He clerked for Supreme Court Justice Ruth Bader Ginsburg in 2000 and worked for the San Francisco Unified School District and U.S. Department of Education during the Clinton administration.