(CNN) Paul Manafort's legal defense team, in one of its last opportunities to hit back at prosecutors, taunted special counsel Robert Mueller for not bringing a case that tied the former Trump campaign chairman to Russian government interference in the 2016 election.

Manafort's defense team emphasized in its sentencing memo that the special counsel's office hasn't charged him with any illegal coordination with Russian government officials in 2016, a major part of Mueller's investigation that the prosecutors previously argued could have arisen from Manafort's extensive Ukrainian connections.

"As said at the beginning of the case, there is no evidence of Russian collusion," Manafort's lawyers wrote in the court filing Monday night.

Manafort's guilty plea included admissions that he had orchestrated a money laundering scheme and committed years of criminal activity as a lobbyist for Ukrainian politicians who hid millions of dollars of that income from the federal government. The charges and admissions didn't touch his work while campaign chair.

His defense lawyers argued that Manafort would have never been prosecuted as harshly had it not been for Deputy Attorney General Rod Rosenstein's appointment of Mueller in May 2017.

"Indeed, it is fair to say that, but for the appointment of the Special Counsel and his Office's decision to pursue Mr. Manafort for a rarely prosecuted FARA violation, Mr. Manafort would not have been indicted in the District of Columbia," the defense team writes.

Under Mueller, Manafort's foreign lobbying violations "went from what was historically an administrative inquiry and proceeding to a federal criminal case and the public vilification of the defendant," the defense team wrote.

"The Special Counsel's attempt to portray him as a lifelong and irredeemable felon is beyond the pale and grossly overstates the facts before this Court."

Arguing for a lighter sentence

Manafort's defense team Monday outlined its argument for the former Trump campaign manager serving less than the 10-year maximum total when he receives his second criminal sentence next month from a federal judge.

In a sentencing memo, Manafort's legal team also revealed how the court's probation office had calculated that his crimes -- including conspiracy and obstruction of justice -- for which he was charged in DC District Court deserve 15 to 20 years in prison. Manafort pleaded guilty to his crimes as a part of a cooperation agreement.

"His case is not about murder, drug cartels, organized crime, the Madoff Ponzi scheme or the collapse of Enron," Manafort's defense attorneys wrote Monday. The mention of Enron especially attacks leads prosecutor Andrew Weissmann, who also led that major corporate investigation.

"Rather, at its core, the charges against the defendant stem from one operable set of facts: Mr. Manafort made a substantial amount of income working as a political consultant in Ukraine, he failed to report to the government the source and total amount of income he made from those activities, and he attempted to conceal his actions from the authorities. He has accepted full responsibility by pleading guilty to this conduct," Manafort's lawyers wrote.

Manafort's lawyers ask that his sentence in DC run alongside his sentence in Virginia, for which prosecutors have requested up to 25 years in prison, instead of stacking the two sentences consecutively. He will be sentenced in Virginia by a federal judge on March 7 for eight financial fraud convictions at a jury trial.

Manafort has been in jail since June 2018 for a witness tampering allegation to which he admitted. He will turn 70 on April 1, making any sentence of two decades or more likely one for which he'll be imprisoned the rest of his life.

Family and friends beg for leniency

Letters Manafort's family and friends wrote on his behalf paint the imprisoned former political operative as a successful, generous and empowering colleague and father -- and an asset to Donald Trump's presidential campaign.

"Paul came to the Trump Presidential Campaign in early 2016 genuinely believing he could assist in helping elect an extremely unconventional GOP Candidate," one friend and colleague, Doug Davenport, wrote to Judge Amy Berman Jackson. "He never deviated—day in/day out—from the sole mission he had been brought in to help achieve: a solid RNC Convention Delegate Operation and a secure GOP Presidential nomination for Donald Trump. ... Paul was simply an easy lightning rod to go after for detractors of Candidate—and now President—Trump."

Manafort's lawyers say their client should be credited for his service to foreign nations as a lobbyist, in past presidential administrations and on presidential campaigns, including Trump's. They note he took no pay while working for Trump -- a notion that prosecutors have raised as suspicious throughout his case.

"Mr. Manafort has spent a lifetime promoting American democratic values and assisting emerging democracies to adopt reforms necessary to become a part of Western society," his defense team writes about his lobbying.

In other letters to the judge submitted Monday, his wife, Kathleen, called him "the rock the family has relied on for years."

"I love him very much," she wrote. She attended nearly all of his major court hearings and his three-week criminal trial in summer 2018 for financial fraud, in which he was first convicted.

His daughter, other relatives and a neighbor who testified against him at his Virginia trial also wrote to Jackson, asking for mercy. One friend noted how Manafort coached youth basketball; another described how Manafort served as an altar boy in elementary school.

One of Manafort's longtime closest colleagues, Rick Gates, did not submit a letter -- not a surprise, given that Gates flipped against his former boss after also facing charges from Mueller and testified against him at trial.

Manafort's health is declining, especially since he's suffered from gout in his right foot since he's been jailed. At his last court appearance, he walked with a cane. At one point while in custody in the past eight months, the defense team revealed, Manafort was treated at Alexandria Hospital. His attorneys note that doctors are looking into a thyroid problem he may have as well.

The filing Monday night mostly glosses over the most notable development since Manafort was convicted last year -- that he lied to prosecutors during his cooperation interviews and to a federal grand jury. His defense team notes on Monday that he was truthful during the "majority" of his 50 hours of interviews.

Manafort's sentencing in the DC case is scheduled for March 13.

This story has been updated.