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Nearly a week after President Bush commuted the prison sentence of I. Lewis "Scooter" Libby, congressional Democrats advanced theories for the clemency.

Rep. John Conyers Jr. (D-Mich.), chairman of the House Judiciary Committee, suggested that the action was aimed at protecting other administration officials. "I think we should put it on the table right at the beginning . . . the suspicion was that if Mr. Libby went to prison, he might further implicate other people in the White House," Conyers said on ABC's "This Week."

(White House spokesman Tony Fratto later told the Associated Press that Conyers's remark was "a fairly ridiculous and baseless assertion.")

Last Monday, Bush commuted Libby's 2½-year prison term for lying to prosecutors in the CIA leak case, leaving other elements of Libby's sentence -- a $250,000 fine and two years of probation -- intact.

On CBS's "Face the Nation," Sen. Charles E. Schumer (D-N.Y.) argued that Bush chose that course of action, rather than issuing a pardon, to provide Libby greater protections against testifying before Congress. "If there were a pardon, Libby could be called before Congress to testify on a whole bunch of things," Schumer said. "Commutation makes it much, much harder to do that."

The leaders of the Senate Judiciary Committee, Sen. Patrick J. Leahy (D-Vt.) and Sen. Arlen Specter (R-Pa.), indicated on CNN's "Late Edition" that they want Libby prosecutor Patrick J. Fitzgerald to testify about his investigation of the CIA leak.

Meanwhile, Conyers said he would pursue contempt-of-Congress charges against the president if the White House refuses to allow former officials to testify regarding the firing of nine U.S. attorneys, echoing statements by Leahy.

On CBS, Sen. Orrin G. Hatch (R-Utah) defended the administration, saying it is "asserting executive privilege properly."

By Zachary A. Goldfarb