A battle is intensifying in the Senate over the appeals court nomination of Goodwin Liu, a law professor at the University of California at Berkeley whom some Democrats consider a potential nominee one day to the Supreme Court.

Democrats vowed Wednesday to press ahead with plans for an April 16 Judiciary Committee hearing on the nomination to the U.S. Court of Appeals for the Ninth Circuit. A day earlier, the GOP demanded a delay and suggested that Liu's nomination might be in jeopardy because he had not provided enough information to the panel.

Activists on both the left and right view Liu's nomination as a practice run for the next Supreme Court vacancy, which could come as soon as this year if Justice John Paul Stevens retires.

On Tuesday, Liu sent 117 items to the committee, a "supplement" to an earlier questionnaire he filled out about his record, including articles he wrote and events in which he participated, but did not include in his original submission.

The committee's seven Republicans -- led by ranking member Jeff Sessions (Ala.) -- responded with a scathing letter to panel Chairman Patrick J. Leahy (D-Vt.).