CHICAGO (CBS) — A day after former Gov. Rod Blagojevich reports to prison to begin his 14-year sentence on corruption charges next week, his former chief of staff will be in front of a federal judge, making his plea for leniency for his role in the Blagojevich case.

John Harris was arrested the same day as Blagojevich on Dec. 9, 2008, when the feds accused him of scheming to sell or trade an appointment to the U.S. Senate. Unlike his boss, Harris began resigned as chief of staff shortly after his arrest, began cooperating with federal investigators within days, and eventually became the star witness at Blagojevich’s two trials.

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In a pre-sentencing filing submitted this week to U.S. District Judge James Zagel – who presided over Blagojevich’s trials – Harris’ attorney Terry Ekl argued Harris should be sentenced to unsupervised probation in light of his guilty plea and cooperation with the feds.

“Mr. Harris has acknowledged his full and complete responsibility for his conduct through his guilty plea, his execution of the plea agreement and, most importantly, his truthful testimony before this Court during the two trials of Defendant Rod Blagojevich,” Ekl wrote.

Harris spent a total of ten days on the witness stand at Blagojevich’s to trials, as the government’s chief witness against Blagojevich, a factor which should certainly work in his favor at his sentencing hearing on March 16.

He has pleaded guilty to a single count of wire fraud, which carries a maximum sentence of 20 years in prison.

In his sentencing positioning paper, Harris’ attorney notes his 4 ½ years of service in the U.S. Army, including more than a year as a judge advocate general in Turkey during the Gulf War, as well as his numerous military awards.

“John Harris’ life contains numerous examples of exemplary achievements attained through hard work, dedication and honesty. Simply stated, he is a good person,” Ekl wrote. “Every aspect of John’s background demonstrates to this court that he is a person of high character and morality. John’s involvement with former Governor Blagojevich is an aberration in the life of a man who exemplifies character and dedication.”

Harris’ attorneys also presented letters from more than 40 friends and colleagues who urge Zagel to show leniency at sentencing.

Former Library Commissioner Mary Dempsey praised Harris for providing thoughtful counsel, and said he was “completely dedicated to doing what was legal, ethical and right.”

State Sen. John Millner (D-Carol Stream) wrote “I have known few men in my time who are as committed to family, community and country as John Harris.”

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Former CTA President Frank Kruesi wrote, “He never has made excuses or elected to shift blame to others … I believe John still has much to contribute to his community.”

Former Illinois State Police Director Larry Trent wrote, “John Harris is a good and decent man who made an error in judgment and who has already paid a very dear price.”

And Chicagoland Chamber of Commerce president Gerald Roper wrote, “I have no doubt the positive impacts that resulted from his work has made us a better city and state.”

Harris’ attorney also pointed to a pre-sentencing report from the federal Probation Department, which notes there was no evidence that Harris did anything illegal for his own personal gain, but instead that he was working at the direction of his boss.

Ekl also argued that Harris took a number of steps to try to deter Blagojevich’s misconduct, including telling the former governor he shouldn’t try to make a deal for a Senate appointment, that he refused to ask then-Illinois Senate President Emil Jones to give Blagojevich the money from his campaign fund in exchange for the Senate seat, and that he told Blagojevich he couldn’t accept campaign cash in exchange for appointing Congressman Jesse Jackson Jr. to the Senate.

“None of the arguments presented by counsel in connection with sentencing are intended to minimize Mr. Harris’ personal regret, embarrassment and sincere contrition for his conduct,” Ekl wrote. “John will forever have to bear the burden of explaining to his three sons and future employers what he did and why he was prosecuted in a criminal case which received national media exposure. John has already paid a great price for his misconduct.”

Harris’ filing also takes a shot at Blagojevich’s actions after his arrest, noting Harris “did not attempt to support his family by appearing on reality shows.” Blagojevich appeared on Donald Trump’s “Celebrity Apprentice” TV show and his wife, Patti, appeared on another reality show in Costa Rica, eating bugs on the show “I’m a Celebrity, Get Me Out of Here.”

After resigning from his job as Blagojevich’s aide, Harris took a job, as an apprentice electrician working on high power lines.

Harris’ cooperation should help him at sentencing, since judges typically show leniency to defendants who have cooperated with federal prosecutors; especially when they plead guilty and testify against a co-defendant, without ever challenging the charges they face themselves.

Another witness from the first Blagojevich trial, Democratic fundraiser Joseph Cari, was sentenced to 3 years of probation last summer. Like Harris, he cooperated with the federal investigation of Blagojevich and testified against the former governor in exchange for leniency. Prosecutors decided not to call Cari as a witness at the second trial, which resulted in Blagojevich’s convictions on multiple counts, including trying to sell or trade a U.S. Senate appointment.

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–Todd Feurer, CBS Chicago Web Producer