Disgraced former U.S. Rep. William Jefferson has found new fuel for a bid to overturn his conviction and 13-year federal prison sentence in a recent U.S. Supreme Court ruling that sets narrow limits on what can be considered an "official act" in political corruption cases.

But Jefferson, now 69 and not due to be released from federal prison until 2023, still faces a difficult road.

Because his normal appeals have run out, legal experts say he must surmount a higher bar than the one former Virginia Gov. Bob McDonnell hurdled when the high court's eight justices unanimously agreed in June to vacate his conviction and federal prosecutors then declined to retry him. 

Attorneys for Jefferson filed a motion last month to toss out his conviction and prison sentence. in it, they said the jury that convicted the former New Orleans congressman of corruption relied on virtually the same, now-discredited definition of an official act that tripped up McDonnell, resulting in a tainted verdict.

Jefferson, now incarcerated at a low-security federal prison in Oakdale, is far from alone among convicted public officials angling for a reprieve in the wake of the McDonnell ruling. Former St. Tammany Parish District Attorney Walter Reed, to name one, invoked the ruling last week in his bid for a new trial.

But legal observers say Jefferson may hold an edge: His case sprang from the same federal circuit court in Virginia as the McDonnell case, in which an appeals court panel last year found that "to a large extent," the jury instruction in McDonnell's case "echoed" the one given in Jefferson's trial.

And the U.S. Supreme Court found that jury instruction, at least in McDonnell's case, went way too far.

"Certainly, Jefferson's filing has both legal appeal and visceral appeal," said Harry Rosenberg, a former U.S. attorney in New Orleans. "I think it's more than just a long shot for Jefferson to get some relief."

Rosenberg noted that Jefferson's attorneys had repeatedly raised the same issue to no avail before and after his 2009 trial — a factor that could weigh in his favor.

Despite the infamous $90,000 in cash found in Jefferson's freezer, his attorneys argued, the government wildly stretched a theory of what constitutes official business in Congress.

The jury convicted Jefferson on 11 of the 16 counts he faced, including bribery, "honest services" wire fraud, money laundering and racketeering. A federal appeals court later upheld his convictions on 10 of those counts. Unlike in McDonnell's case, the U.S. Supreme Court declined to hear Jefferson's appeal.

The charges against Jefferson related largely to allegations that — in exchange for payments to himself and family members — he made introductions and helped swing business deals between Americans and government officials in western Africa.

Prosecutors offered evidence that Jefferson wrote to the African officials on his congressional letterhead, that his staff arranged trips there and that Jefferson set up meetings with foreign and U.S. agency officials in a scheme with his alleged bribers.

Those actions may not have involved legislation or other formal action in Congress, but they fell under the practice known as "constituent services," prosecutors maintained.

U.S. District Judge T.S. Ellis agreed, instructing the jury that an "act may be official even if it was not taken pursuant to responsibilities explicitly assigned by law."

The U.S. Supreme Court insisted on a narrower definition in the McDonnell decision. An official act is a decision on a specific issue that "must involve a formal exercise of governmental power," Chief Justice John Roberts wrote in the court's unanimous opinion. "Setting up a meeting, talking to another official or organizing an event — without more — does not fit that definition of 'official act.' "

A jury found McDonnell guilty on 11 counts related to his and his wife's acceptance of more than $175,000 in loans and gifts that included a Rolex watch, a $20,000 shopping spree and vacations from a businessman seeking help in promoting a dietary supplement.

Jefferson's attorney, Robert Trout, declined to comment on the parallels between the two cases. But in his motion to vacate Jefferson's conviction, Trout argued that the bad jury instruction in Jefferson's case tainted the entire trial.

"In short, the bulk of the government evidence, and the theory of the prosecution’s case, depended largely on what Mr. Jefferson did in Africa to influence African government officials," he wrote. "There can be no doubt that the jury was invited to convict Mr. Jefferson for these activities, and also no doubt that they do not constitute official acts under (the) McDonnell (ruling)."

Jefferson had appeared to reach the end of the line in appealing his 2009 conviction when the U.S. Supreme Court declined to review his case in 2012.

Loyola law professor Dane Ciolino said Jefferson's renewed challenge "seems on its face to have some merit, and it's certainly not frivolous."

"You can't underestimate the significance of that McDonnell opinion. It does very narrowly define what an official act is," Ciolino said. "And of course, what the government argued in Jefferson's case were (definitions of) official acts that were much broader than those allowed in McDonnell."

The key difference, Ciolino said, is that Jefferson's normal appeals had run out. Jefferson has "a shot," he said, but such post-conviction motions are inherently difficult to win.

"It's not just a matter of showing the jury charges were inconsistent (with the McDonnell decision). He's got to show significant prejudice or deep structural error that undermines confidence in the whole fact-finding process at trial," Ciolino said.

Ellis, a judge in the Eastern District of Virginia, has ordered the government to respond to Jefferson's motion by Halloween. Jefferson's attorneys then will have another week to respond. It's unclear when Ellis, who was nominated by President Ronald Reagan, will rule on the motion.

Follow John Simerman on Twitter, @johnsimerman.