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The president tapped Mr. Liu more than a year ago to fill a vacancy on the 9th Circuit, which includes California and much of the rest of the West. His nomination stalled in the Senate amid Republican opposition, and Mr. Obama renominated him for the post in January.

The SenateJudiciary Committee in April voted 10-8, entirely along party lines, to send Mr. Liu’s nomination to the full Senate.

All 24 judicial nominations sent to the full Senate this year have been confirmed. The tally includes 21 district and three Circuit Court nominees.

The Liu debate extends far beyond Capitol Hill, as liberal, ethnic-minority and conservative groups see the nomination fight as a crucial test of the president’s ability to put his stamp on the nation’s judiciary.

“As much as I know some conservatives have enjoyed using him to raise money, he’s really not the wild progressive that they’re trying to make him out to be,” said Karen K. Narasaki, president and executive director of the Asian American Justice Center.

Ms. Narasaki added Republicans risk retribution at the polls from Asian-Americans if they oppose Mr. Liu, who was born in Augusta, Ga., of parents who immigrated from Taiwan.

“It’s going to be seen in the next election as an indication the party is actually not supportive of the Asian-American community,” she said. “This has more visibility across the country in the Asian-American community than any nominee I’ve seen, and I’ve been in Washington for 20 years.”

But Curt Levey, executive director of the conservative Committee for Justice, has called Mr. Liu “the worst of Obama’s nominees at all levels of the federal courts.”

Mr. Liu has attracted some support outside Democratic circles, including from Kenneth W. Starr, the independent counsel during President Clinton’s Whitewater and Monica Lewinsky scandals.

Richard Painter, who served as counsel to President George W. Bush, also has spoken favorably of the professor.

“In short, Goodwin is a person of great intellect, accomplishment and integrity, and he is exceptionally well-qualified to serve on the court of appeals,” Mr. Starr said in a joint letter written in 2010 with Akhil Reed Amar, a Yale Law School professor, to the party leaders of the SenateJudiciary Committee.

“The nation is fortunate that he is willing to leave academia to engage in this important form of public service.”