WASHINGTON – Senate Republicans mounted a concerted attack Friday on federal appeals court nominee Goodwin Liu in a session that both parties see as a warm-up for the coming fight to replace Justice John Paul Stevens on the Supreme Court.

Liu, an associate dean at the University of California at Berkeley law school, is being vetted by the Senate Judiciary Committee for a slot on the 9th Circuit Court of Appeals, which covers nine Western states. Groups on the left strongly support him and many on the right oppose him for the same reason: Liu is an outspoken liberal whose writings have promoted the idea that interpreting the Constitution requires much more than just divining the intent of the Founding Fathers.

In their interrogation of Liu, Senate Republicans are testing arguments they will use when President Obama nominates a successor to Stevens, who has declared his intention to step down from the high court in the coming months.

Many Democrats are hoping that Obama will name an outspoken liberal in the mold of Liu, and plan to mount a vigorous defense of the 9th Circuit nominee to demonstrate that such a candidate can clear the Senate gantlet.

At the hearing, Judiciary ranking member Jeff Sessions, R-Ala., made clear his belief that Liu’s writings “represent, I think, the very vanguard of what I would call intellectual judicial activism.”

Sessions said Liu would look at the Constitution and “find rights there that have never been found before.”

Liu parried Republicans’ charges with nuanced answers, saying he found both the “originalist” and “judicial activist” labels insufficiently precise to be useful. Liu said the original intent of the Constitution’s framers was “very important” for judges to consider, but “it is not the sole touchstone” of legal interpretation.

Faced with Republicans’ citation of several potentially controversial passages in his past writings, Liu made clear that there was a difference between his duties as a law professor and scholar versus what his responsibilities would be on the bench.

Republicans, particularly Sen. Jon Kyl, R-Ariz., were critical of Liu for his past opposition to the Supreme Court nominations of John Roberts and Samuel Alito. They focused on a passage from Liu’s testimony to the Judiciary Committee during Alito’s confirmation, which read: “Judge Alito’s record envisions an America where police may shoot and kill an unarmed boy to stop him from running away with a stolen purse; where federal agents may point guns at ordinary citizens during a raid, even after no sign of resistance where a black man may be sentenced to death by an all-white jury for killing a white man.”

“This calls into question your judicial temperament,” Kyl said, later adding: “I see it as very vicious and emotionally and racially charged. Very intemperate.”

Liu acknowledged using “overly flowery language” but largely stood by his comments. He also compared himself to Alito, noting that both are from immigrant families and have worked their way up from humble origins.

Liu himself is seen in some quarters as a potential future candidate for the Supreme Court. The son of Taiwanese immigrants, Liu was a Rhodes scholar and Supreme Court clerk before assuming his current position at Berkeley.

No Asian American has ever served on the Supreme Court, nor are there any Asian Americans among the active judges on the U.S. circuit courts of appeal.