Acting as his own attorney, former New Orleans Mayor C. Ray Nagin filed a new motion this week asking a federal judge to overturn his conviction on 20 counts related to allegations that he traded his political influence for bribes from city contractors.

Nagin's motion, typed at a federal prison camp in Texarkana, Texas, where he is serving a 10-year sentence, cites the same U.S. Supreme Court precedent that led a Virginia judge last week to vacate most of the charges that landed another disgraced New Orleans politician — former U.S. Rep. William Jefferson — in the federal pen.

Jefferson was ordered freed pending a new sentencing on three remaining counts.

Nagin, 61, who struck out in an earlier appeal, argues that the high court's unanimous decision last year in the case of former Virginia Gov. Bob McDonnell applies equally to him.

In that case, the Supreme Court set strict limits on what qualifies as an illegal quid pro quo in politics, narrowing the definition of an "official act" when it comes to political corruption.

Nagin also cites a federal appeals court panel's decision this year that overturned the corruption conviction of Sheldon Silver, the former speaker of the New York State Assembly, on the same grounds.

"The fundamentals of my case are practically identical" to the McDonnell and Silver cases, Nagin argues.

"The central issue is did the governor, state assembly leader or myself engage in official acts IN EXCHANGE FOR any contractor largess. The answer is no."

The former mayor goes on to claim that nothing he did for Covington businessman Frank Fradella, Nagin's most prolific source of bribes and the star witness against him, amounted to a quid pro quo.

Echoing an argument he made at his trial in 2014, Nagin says, for instance, that his signing of city contracts awarded to Fradella's company amounted to mere ministerial acts.

"At no time did I 'put my thumb on the scale' to tip these contracts to Mr. Fradella or anyone else," Nagin writes. "I do recall a meeting to encourage some lenders to provide a line of credit to his company but stressed that as long as he was the lowest, responsive bidder there was plenty of recovery work for firms like his. I never made any promises."

In 2012, Fradella admitted he had funneled roughly $200,000 in cash and gifts to Nagin over several years, including $112,500 in nine monthly “consulting payments” made to the mayor after Nagin's exit from City Hall.

Fradella also testified to providing the Nagin family’s business with two truckloads of free granite and $50,000 in cash that was routed through a trust.

In his 11-page motion, Nagin downplays his own role in his sons' dealings with Fradella on behalf of the family business. He also argues that the consulting contract he received after he left office was legitimate and came while Fradella was no longer an officer or stockholder in the firm that awarded the contract. 

Nagin also notes news reports about an arrest warrant issued in Florida in January that accuses Fradella of orchestrating a money-laundering and stock-fraud scheme centered on a Colorado marijuana business.

Nagin argues that Fradella's alleged chicanery took place "right under the noses of federal prosecutors" who "knew or should have known" about it and failed to reveal it.

Nagin's trial attorney, Robert Jenkins, could have used such information to impeach Fradella as a witness at his trial, the former mayor says, arguing that he was the victim of both prosecutorial misconduct and an ineffective lawyer.

He cites wide criticism over Jenkins' handling of his trial, but also claims that Jenkins "repeatedly ran into various intimidation tactics being used by prosecutors on potential witnesses we wanted to call."

Jenkins' closing argument was "quite rambling and lacked clarity," Nagin writes. He suggests that Jenkins fell off his game after a prosecutor threatened him in the courthouse hallway during the trial.

Nagin ignores the rest of the allegations that resulted in his conviction, however, including bribery schemes involving other city contractors.

The jury found Nagin guilty on all but one of the 21 counts he faced, making him the first New Orleans mayor to be prosecuted and convicted for corruption.

A federal appeals court panel rejected Nagin's appeal in early 2016. Nagin petitioned the U.S. Supreme Court to take up the case in April 2016, two months before the high court issued its ruling in the McDonnell case. The high court denied Nagin's petition in October 2016.

Nagin is due for release from federal prison in 2023.

His case was reassigned Thursday to U.S. District Judge Jane Triche Milazzo. Judge Helen "Ginger" Berrigan, who presided over Nagin's trial, retired last year.

Follow John Simerman on Twitter, @johnsimerman.