WASHINGTON (CNN) -- The top aide to White House political adviser Karl Rove refused to answer at least a dozen questions from a Senate committee Thursday about the firings of eight U.S. attorneys last year, asserting -- as expected -- a claim of executive privilege by President Bush.

Jennings, right, consults with attorney Mark Paoletta before declining to answer a question.

Scott Jennings, who also is a special assistant to Bush, arrived at the Senate Judiciary Committee hearing with his attorney, Mark Paoletta, to avoid a contempt citation.

The panel had subpoenaed both Jennings and Rove, but Rove refused to show up, angering Chairman Patrick Leahy, D-Vermont.

"I consider that blanket claim (of executive privilege) to be unsubstantiated," Leahy said he told Jennings before the meeting.

White House Counsel Fred Fielding had informed the Judiciary Committee on Wednesday that Rove, "as an immediate adviser to the president," can't be ordered to testify and was told not to attend.

Sen. Dick Durbin, D-Illinois, asked Jennings, "Where is Karl Rove? Why is he hiding? Why does he throw a young staffer like you into the line of fire while he hides behind the White House curtains?"

The White House says it is trying to protect the president's ability to receive candid advice and offered to let top aides discuss the firings only if they were not placed under oath and no transcript was taken.

The senators sought answers about e-mail sent by dozens of White House staff using e-mail accounts provided through a Republican National Committee Internet address.

In March, congressional investigators found evidence that White House staffers had used those e-mail accounts to discuss government business -- including the firings of the U.S. attorneys -- in violation of the Presidential Records Act. The law is aimed at keeping government business separate from partisan political activities.

Last month, the House Judiciary Committee expanded its executive privilege fight with the White House to the RNC, formally demanding information from the RNC e-mail accounts.

Leahy asked Jennings why he had used his RNC e-mail account to set up a conference call to discuss U.S. Attorney Tim Griffin.

In June 2006, the Justice Department informed Bud Cummins, then-U.S. attorney for the Eastern District of Arkansas, that he would be replaced by Tim Griffin, a former lieutenant of Rove who had recently returned from service as a military lawyer. Griffin began the job in December as an interim federal attorney. He resigned in June as the controversy increased.

Jennings replied: "Senator, pursuant to the president's assertion of executive privilege over consideration, deliberations or communications related to the U.S. attorneys matter, I must respectfully decline to answer your question at this time," an answer that he gave on many times during his testimony. As Jennings repeatedly refuses to answer, he's accused of getting paid to 'stonewall' »

Jennings also was asked whether he had sent an e-mail to Monica Goodling, then-counsel to Attorney General Alberto Gonzales, about New Mexico U.S. Attorney David Iglesias, who was fired late in 2006.

Jennings worked for the president's re-election campaign in New Mexico in 2004.

"Were you in contact in that capacity with Monica Goodling at the Department of Justice?" Durbin, D asked.

Jennings: "No, not that I recall."

Durbin: "Were you aware of any conversations by members of Congress or members of the White House staff with Mr. Iglesias about the conduct of his office in New Mexico?

Jennings: "No, I'm not aware of any conversations that were taking place."

When Jennings was quizzed about whether he had communicated with Goodling via e-mail about New Mexico politics after he had worked in that state, he said he couldn't recall.

Durbin then pulled out an e-mail exchanged between Jennings and Goodling in June 2006, and asked Jennings to explain it. Jennings declined, invoking executive privilege.

According to Gonzales, Republican Sen. Pete Domenici, New Mexico's senior senator, complained to Gonzales about Iglesias in the fall of 2005, saying the U.S. attorney "was in over his head." Iglesias contends Domenici wanted him to push harder on a corruption probe of state Democrats before last November's midterm elections.

Jennings said he began using the RNC e-mail system because it was always available to him. Eventually, he added, it became a kind of "default" e-mail address.

Sen. Arlen Specter, the committee's ranking Republican, who has sharply criticized Gonzales and repeated his desire to "end his tenure," pushed to have Leahy agree to join Specter and other congressional leaders who seek a meeting with Bush in an effort to resolve the controversy over the firings.

But Leahy replied to the suggestion of resolving the impasse with, "If I thought that there was any willingness to work it out instead of stonewalling, I would feel a lot better about this."

The privilege claim can be challenged in court. But Specter has said the courts would be unlikely to resolve any challenge before Bush leaves office.

Vice President Dick Cheney dismissed the congressional investigation of the attorney firings as a "witch hunt" during a CNN interview Tuesday. Democratic congressional leaders, however, say administration officials have been unable to answer their most basic questions -- who compiled the list of prosecutors to be dismissed, and why were they selected?

"It is regretted that the committee has forced this action, as the president's offer of accommodation to you and to the House Judiciary Committee could have provided information being sought in a manner respectful of presidential prerogatives and consistent with a spirit of comity," Fielding wrote.

But Sen. Patrick Leahy, D-Vermont, accused the White House of trying to cover up Rove's role in the firings. He questioned why Rove discussed the matter publicly when the issue first made news, but now "is suddenly unable to talk it about when he is under oath."

"Mr. Rove has given reasons for the firings that have now been shown to be inaccurate, after-the-fact fabrications," Leahy said in a statement issued Wednesday evening. "Yet he now refuses to tell this committee the truth about his role in targeting well-respected U.S. attorneys for firing and in seeking to cover up his role and that of his staff in the scandal."

Mark Paoletta, a lawyer for Jennings, told CNN his client will appear before the Judiciary Committee but would refuse to answer questions he feels are covered by executive privilege. Former White House political director Sara Taylor testified under similar circumstances in July.

The White House already has invoked executive privilege to block previous testimony by Taylor and former White House counsel Harriet Miers, who skipped a hearing in the House two weeks ago, and to keep Chief of Staff Josh Bolten from turning over documents subpoenaed as part of the inquiry.

The panel voted to cite Miers and Bolten for contempt of Congress for failing to comply with subpoenas. The decision on whether to pursue any action on those citations lies with the Justice Department.

The privilege claim can be challenged in court. But Sen. Arlen Specter of Pennsylvania, the ranking Republican on the Judiciary Committee, has said the courts would be unlikely to resolve any challenge before Bush leaves office.

Vice President Dick Cheney dismissed the congressional investigation of the attorney firings as a "witch hunt" during a CNN interview Tuesday. Democratic congressional leaders, however, say administration officials have been unable to answer their most basic questions -- who compiled the list of prosecutors to be dismissed, and why were they selected?

While the Bush administration has maintained that the prosecutors' firings were handled properly, the controversy has led to the resignations of at least three top Justice Department officials and triggered widespread criticism of Attorney General Alberto Gonzales, who repeatedly told a Senate committee in April that he did not recall details of the firings.

Critics say the attorneys were forced out for political reasons, such as for failing to bring voter fraud cases pushed by Republican activists, and administration officials have acknowledged that one was fired to allow a Rove protege to take a post in Arkansas. E-mail to a friend

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