SPRINGFIELD - In what may serve as an epilogue to one Illinois corruption scandal and a prologue to another, the U.S. Supreme Court has declined to hear the appeal of imprisoned former Gov. George Ryan.

The high court's announcement - made without explanation early Tuesday - is likely the final word in an epic political drama that has transformed the state's political landscape. Barring unlikely presidential action, it means the 74-year-old Republican probably will have to serve the remainder of the 6 1/2-year federal prison term he began last year for fleecing the state during his long political career.

"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," U.S. Attorney Patrick Fitzgerald, Chicago's top federal prosecutor, said in a statement Tuesday.

Ryan's defense attorney, fellow former Republican Gov. James R. Thompson, acknowledged that the legal fight is over. He said he will seek a commutation from President George W. Bush.

"We recognize that the judicial process has come to an end for Gov. Ryan and there will be no more court review," Thompson said. "We think that the next appropriate step is to ask the president of the United States for executive clemency."

Ryan was convicted of racketeering and fraud in 2006 for steering state contracts to friends and associates in exchange for cash, gifts and vacations. He had claimed his Chicago trial was compromised by a tainted jury. The Chicago-based 7th U.S. Circuit Court of Appeals earlier upheld the convictions.

Ryan is serving his sentence at a minimum-security federal facility at Terre Haute, Ind.

Ryan's health problems, including Crohn's disease and diabetes, could justify a commutation of his sentence by Bush when his term ends in January, said Brian Gaines, political scientist at the University of Illinois at Champaign-Urbana.

But Gaines also noted that Ryan wasn't part of Bush's inner circle of political friends and allies. And Ryan's historic moratorium on executions in Illinois, which endeared him to anti-death-penalty advocates around the world, wasn't viewed so favorably by Bush Republicans.

"You never can be sure … (but) if I had to bet my life's savings, I'd say it's a long-shot," Gaines said.

Ryan, a gruff, cigar-chomping pragmatist from the old-school tradition of Illinois politics, spent 40 years in various elective posts. In his final few years in office, he watched federal prosecutors convict ever-higher-ranking associates on corruption charges. His one term as governor, from 1999 to 2003, was besieged by open speculation about how far up the ladder the investigation would go - essentially the same situation Gov. Rod Blagojevich is in now.

Tuesday's final rejection of Ryan's appeal comes as another federal jury huddles in the same Chicago federal courts building, deliberating the fate of Antoin "Tony" Rezko. He is accused of squeezing state contractors for bribes, using his clout as a confidante of Blagojevich, Ryan's Democratic successor.

Blagojevich hasn't been charged with any crime. But his administration has been hobbled by the ongoing investigation.

"We've seen a history of Illinois politicians betraying the public trust even as they've watched former colleagues go off to prison," said Mike Lawrence, former press secretary to ex-Gov. Jim Edgar.

Lawrence noted that, long before ex-Gov. Thompson defended ex-Gov. Ryan on corruption charges, Thompson led the prosecution that sent ex-Gov. Otto Kerner to prison in 1973. This was also well before then-Gov. Dan Walker would start his own prison term.

"Rod Blagojevich got elected because George Ryan was enveloped by scandal," said Lawrence, who is now head of the Paul Simon Public Policy Institute at Southern Illinois University at Carbondale. "Yet it's clear that people around Blagojevich put themselves in the position of drawing the attention of federal prosecutors, almost immediately … It blows my mind."

Kevin McDermott can be reached at kmcdermott@post-dispatch.com. The Associated Press contributed to this report.