U.S. attorney Fitzgerald may be called to testify about his prosecution of a former vice presidential aide, I. Lewis “Scooter” Libby, Senator Leahy of Vermont said.

Mr. Leahy, the Judiciary Committee chairman, and Senator Specter, the ranking Republican on the panel, indicated that they want to discuss sentencing guidelines in light of President Bush’s commutation of Libby’s sentence and also to quiz Mr. Fitzgerald on his handling of the case.

“I still haven’t figured out what that case is all about,” Mr. Specter said. “There are a lot of ramifications that I think we ought to go into. Why were they pursuing the matter long after there was no underlying crime on the outing of the CIA agent? Why were they pursuing it after we knew who the leaker was?”

Mr. Leahy, appearing with Mr. Specter of Pennsylvania on CNN’s “Late Edition,” noted they both are former prosecutors and said he has “some of the very same questions in mind.” Smiling, he added: “You might find it to be an interesting hearing.”

Libby was convicted of lying to investigators probing the 2003 leak of Central Intelligence Agency official Valerie Plame’s identity. He resigned as Vice President Cheney’s chief of staff upon being indicted in 2005. Mr. Bush commuted Libby’s 2 1/2-year prison term on July 2, calling the sentence “excessive.”

Senator Schumer, a Democrat of New York, said he urged Mr. Leahy to hold hearings on the issue. Appearing on CBS-TV’s “Face the Nation” program, Mr. Schumer noted that Mr. Fitzgerald, during his investigation, interviewed both Messrs. Bush and Cheney. He “might have some interesting things to say,” Mr. Schumer said. Mr. Leahy said he had no plans to call Libby. Because Mr. Bush did not give Libby “an out-and-out pardon,” he can take the Fifth Amendment and refuse to testify, Mr. Leahy said.

The commutation was “a blatant way of guaranteeing that Scooter Libby would not” disclose “some of the misleading information given out by Vice President Cheney and the president,” Mr. Leahy said. “They led us into this war in Iraq, and they bought his silence.”

Mr. Fitzgerald, in a statement after the commutation was announced, took exception to Mr. Bush’s characterization of the sentence as too harsh.

“It is fundamental to the rule of law that all citizens stand before the bar of justice as equals,” Mr. Fitzgerald said in the statement. “That principle guided the judge.”

The House Judiciary Committee chairman, Rep. John Conyers, called Mr. Bush’s commutation a “step in violation of the rules of sentencing guidelines.” Mr. Conyers, on ABC-TV’s “This Week” program, said, “The president is not supposed to intervene until there has been an exhaustion of the appeals process. Here, the president didn’t wait.”

Mr. Conyers, a Democrat of Michigan, said, “The general impression is” that Mr. Bush commuted Libby’s sentence to keep him quiet. He scheduled a hearing of his committee July 11 on the commutation.

Senator Hatch, a Republican of Utah, said on the CBS program that “the president has an absolute right” to commute sentences.

“I think he should have been pardoned,” Mr. Hatch said of Libby. He added that Mr. Bush’s commutation was “no different from what President Clinton did when he granted 140 pardons and 36 commutations” on his last day in office.

Rep. Chris Cannon, a Republican of Utah, said on “Fox News Sunday” TV program that Libby’s punishment has been stiff enough.

“It’s clear that Scooter’s not going to go to jail, but he’s paid a pretty substantial penalty, a big penalty, $250,000,” Mr. Cannon said. “His career is affected. He’s never going to be the same after having gone through this process.”