Libby was sentenced to five years for lying to a federal grand jury investigating the leak of Valerie Plame's status as a CIA officer.
Presidents traditionally issue a few pardons and commute some sentences just before they leave office and a successor is inaugurated.And were Bush to decide to allow Ryan to leave prison for time served, some political observers say the consideration would be based on Ryan's age and health. Both prosecutors and defense lawyers believe Ryan has a better chance of winning his request for clemency than he did with Tuesday's failed bid to appeal to the Supreme Court.
The justices made no comment as they refused to take up the claim that Ryan had not received a fair trial due to chaotic jury deliberations.
Chicago's top federal prosecutor, U.S. Attorney Patrick J. Fitzgerald, said he was happy the high court decided to let Ryan's conviction stand.
"Mr. Ryan has exhausted every legal avenue and argument afforded him but the verdict stands that he was guilty of corrupting the highest office in the state," Fitzgerald said in a statement.
Ryan was convicted in April 2006 of steering contracts to lobbyists and other friends, tax fraud, misuse of tax dollars and state workers and squelching an investigation of links between bribery and fundraising.
His 37-page petition to the Supreme Court claimed his chances of getting a fair trial were wrecked when U.S. District Judge Rebecca R. Pallmeyer replaced two jurors with alternates after deliberations were well under way. The two jurors were removed for failing to mention of their police records on a pre-trial questionnaire.
Ryan's lawyers also argued the deliberations were tainted after one of the jurors, a substitute kindergarten teacher, brought legal materials she found on the Internet into the jury room in defiance of instructions.
Most of the corrupt activity charged in Ryan's indictment took place when the husky voiced, snowy haired onetime Kankakee pharmacist was Illinois secretary of state before his 1998 election as governor. Also convicted at the trial was businessman Larry Warner, who received leases for himself and clients from the secretary of state's office when Ryan was in charge.
Ryan and Warner filed a joint appeal with the Supreme Court and the high court in refusing to hear Ryan's refused to hear Warner's as well.
Under federal law Ryan can get 15 percent of the sentence off for good behavior.
A former federal prosecutor who represented the government at the Ryan trial said commuting the former governor's sentence would be a mistake.
"When defendants are charged and they are convicted by overwhelming evidence and it is in the context where the public trust was manipulated and violated then I think the conviction should stand," said Fardon, who is now in private practice.
There is no way to tell what Bush might decide about commuting Ryan's sentence but few if any doubt that he will be asked to do so.
Thompson still has influence in Republican politics and is certain to mobilize his network of lawyers, lobbyists and lawmakers in the cause.
One expert, Loyola University political scientist Alan R. Gitelson, said estimated the chances of a commutation at 50-50.
"If (Bush) commutes it, it will be on the grounds of (Ryan's) age and his health," Gitelson said. "Unlike Libby, it will be a humanitarian act."
The high court did not reject Ryan's claim that his trial was unfair. It refused to grant certiorari to the former governor's appeal. That is, it refused even to consider it.
The Associated Press contributed to this report.