Washington ? Atty. Gen. John Ashcroft removed himself Tuesday from the investigation into whether the Bush administration leaked a CIA operative’s name to a newspaper columnist, and a career federal prosecutor from Chicago was named as special counsel to take over.

In a move cheered by Democrats, Deputy Atty. Gen. James Comey announced that Ashcroft had stepped aside to avoid the appearance of a conflict of interest after reviewing evidence recently developed in the inquiry. He would not specify the nature of that evidence.

Comey said U.S. Atty. Patrick J. Fitzgerald in Chicago, a veteran of terrorism and political corruption cases, would take over as a special prosecutor and would be given “the tools to conduct a completely independent investigation.”

“He has the power and authority to make whatever prosecutive judgments he believes are appropriate without having to come back to me or anybody else at the Justice Department for approvals,” Comey said.

Comey, however, will retain ultimate authority over Fitzgerald as the acting attorney general for the case. Comey rejected choosing a complete outsider to be the special counsel.

Investigators want to know who leaked the name of Valerie Plame, an undercover CIA officer, to syndicated columnist Robert Novak in July. Plame is married to former Ambassador Joseph C. Wilson, who has said he believes his wife’s identity was disclosed to discredit his assertions that the Bush administration exaggerated Iraq’s nuclear capabilities to build a case for war.

The leaker could be charged with a felony if identified. The FBI has interviewed more than three dozen Bush administration officials, including political adviser Karl Rove and press secretary Scott McClellan.

Fitzgerald, 43, who recently handled the corruption indictment of ex-Illinois Gov. George Ryan, was hailed by Comey as an “Eliot Ness with a Harvard law degree and a sense of humor.”

With an election year approaching, a vacationing President Bush welcomed the decision from his ranch in Crawford, Texas. The president “wants to get to the bottom of this,” White House spokesman Trent Duffy said.

Democrats, who for months demanded Ashcroft step aside from the politically sensitive probe, likewise applauded the decision.

“It’s (like) a special counsel in every way if you combine the independence he has with the fact that Comey promised me that he would report to Congress if anyone blocked the investigation,” said Sen. Charles Schumer, D-N.Y., an early critic of the probe and a member of the Judiciary Committee.

Comey would not specify what prompted Ashcroft’s decision, which the administration previously had resisted. But he said “it is not one of actual conflict of interest that arises normally when someone has a financial interest or something. The issue that he was concerned about was one of appearance. And I can’t go beyond that.”

The department’s No. 2 official, Comey said he considered and rejected an outside counsel because Fitzgerald has the prosecutorial experience and the knowledge of national security matters that make him “the perfect man for this job.”

Further, Fitzgerald is prepared to assume command without delay and can retain the career prosecutors and FBI agents who have handled the probe so far, or he can make changes in the team, Comey said.