ney, who was convicted of lying to investigators in the C.I.A. leak case and sentenced Tuesday to 30 months in prison.

A pardon for Mr. Libby would attract more painful attention to a case from which Mr. Bush had managed to keep his distance for more than three years, a case inextricably linked to the flawed intelligence used to justify the Iraq war and an administration effort to discredit a critic that ultimately exposed a C.I.A. officer. The Democrats who control Congress would be none too pleased, either.

A decision not to pardon Mr. Libby would further alienate members of Mr. Bush’s traditional base of support in the conservative movement, a group already angry about his proposed immigration policy, his administration’s spending and his approach to Iran.

So far, Mr. Bush seems to be willing to take that chance, saying he will not intervene until Mr. Libby’s legal team has exhausted its avenues of appeal.

Already, major conservative and neoconservative organizations, magazines and Web sites are expressing vexation that Mr. Bush has not granted clemency to Mr. Libby, who they say was unfairly railroaded for an initial leak that has now been traced to Richard L. Armitage, the former deputy secretary of state.

“I don’t understand it,” said David Frum, a former speech writer for Mr. Bush who is now a fellow at the American Enterprise Institute, a conservative research group with close ties to the White House. “A lot of people in the conservative world are weighted down by the sheer, glaring unfairness here.”

A conservative with close ties to the administration, who requested anonymity to speak frankly, put it another way: “Letting Scooter go to jail would be a politically irrational symbol to the last chunk of the 29 percent upon which he stands,” a reference to the low percentage of Americans who tell pollsters they support Mr. Bush.

But Mr. Bush has never been very eager to grant pardons, and in fact is among the stingiest presidents in history, said P. S. Ruckman Jr., a political science professor who studies pardons at Rock Valley College in Rockford, Ill. Mr. Bush took office as his predecessor, Bill Clinton, was facing harsh scrutiny for granting a pardon to Marc Rich, whose former wife, Denise, had donated heavily to Mr. Clinton’s presidential library.

A former senior administration official with his own ties to the case said Mr. Libby had failed to meet the general standard for a pardon by not showing contrition or serving any time. This official also noted that Mr. Libby had also been found guilty of lying to investigators, the same offense that led to the impeachment of Mr. Clinton.

The former official, who requested anonymity to speak frankly about the president, said: “It would show a deep disregard for the rule of law if he was to do it right now, when there has been no remorse shown by a convicted felon and no time has been served. How’s this going to fit in his long-term legacy?”

Though they can be ignored by presidents, the guidelines for pardons and clemency recommended by the Department of Justice say that a convict should generally have to wait five years after conviction or release from confinement before being pardoned. Those who received pardons are also generally expected to accept responsibility for their criminal conduct, and should be seeking forgiveness rather than vindication. Presidents can also commute sentences without granting an underlying pardon, although that action is rare and is generally taken after a sentence has begun.

Kenneth L. Adelman, the former director of the Arms Control and Disarmament Agency and one of Mr. Libby’s prominent supporters, said he did not believe a pardon of Mr. Libby would have any bearing on Mr. Bush’s legacy.

“Clinton is very popular in the world, and he pardoned Marc Rich, of all things,” Mr. Adelman said. (Mr. Rich was a fugitive from charges of conspiracy, tax evasion, racketeering and violating United States sanctions by trading oil with Iran when Mr. Clinton pardoned him.)

Mr. Adelman said he was chagrined by what he described as the president’s inconsistent application of loyalty, which he said seems to be cutting against Mr. Libby after having played out in favor of former Defense Secretary Donald H. Rumsfeld and Attorney General Alberto R. Gonzales, “who were palpably doing a terrible job.”

But Mr. Bush’s support for Mr. Gonzales in the face of charges that the attorney general’s office politicized the hiring and firing of federal prosecutors has not helped clear a path for a pardon for Mr. Libby.

Other presidents withstood calls for pardons from their supporters and survived with their legacies intact.

President Ronald Reagan faced very similar — albeit, pre-Internet — pressure from conservatives to grant pardons to Oliver North, John M. Poindexter and others indicted for roles in the Iran-contra affair. He never did so, leaving the matter to his successor and vice president, George Bush. (Mr. Bush did not grant clemency to Colonel North or Admiral Poindexter, neither of whose convictions stood; he did pardon six others.)

Mr. Bush, who is hoping for a Republican successor, could do the same — and judging by the reactions against the sentence for Mr. Libby at the Republican presidential debate on CNN on Tuesday, Mr. Libby could ultimately get a pardon.

But that would mean withstanding the pressure that will intensify if and when Mr. Libby goes to jail, which could happen in a matter of weeks, even as his appeals are pending. Speaking with reporters with him for the Group of Eight economic summit in Germany on Wednesday, Mr. Bush was not showing his hand. “It wouldn’t be appropriate for me to discuss the case until after the legal remedies have run its course,” he said. He cut off a reporter’s follow-up question on a possible pardon by moving on to another reporter, Terence Hunt of The Associated Press, who changed the subject to the new tensions with Russia. “Nice going, Terry,” Mr. Bush said.

Sabrina Pacifici contributed research.