Federal prosecutors on Tuesday recommended that former deputy Trump campaign chairman Rick Gates serve no prison time, citing his “extraordinary assistance” in special counsel Robert S. Mueller III’s Russia investigation, according to a new court filing.

Prosecutors did not oppose Gates’s request for probation, which could be conditioned on what the government said is his continuing cooperation in several matters that it did not make public.

Gates and his longtime boss, Paul Manafort, were the first individuals publicly charged by Mueller in October 2017 as the special counsel sought to learn whether any Americans conspired with Russian efforts to influence the 2016 election. Manafort served as one of Donald Trump’s campaign chairmen in the 2016 race.

Gates, 47, pleaded guilty in February 2018 to conspiring to conceal proceeds from a decade of lucrative lobbying work that he and Manafort had done for Ukraine and lying to the FBI, and he began cooperating with firsthand insight into several of the president’s senior aides and activities.

Although Manafort resigned from the campaign in August 2016 as word of his Ukraine work surfaced, Gates remained until Election Day, working at one point for the Republican National Committee, and then became deputy chairman of Trump’s inaugural committee.

He is one of six Trump aides or associates convicted in cases from the special counsel probe, but unlike the others, he made repeat appearances in court to bolster federal cases.

In a 19-page filing and a separate, sealed summary, U.S. prosecutors described Gates’s ongoing cooperation and wrote that in addition to testifying in three Mueller-related trials, he met with investigators more than 50 times, voluntarily surrendered electronic devices for broad government searches and gave information used in more than a dozen search warrants.

Gates also voluntarily admitted to criminal conduct of which prosecutors were unaware, and pledged to continue cooperating after sentencing “in several ongoing matters.”

“The government believes he has been entirely candid about his and other’s criminality. His assistance has been substantial,” Assistant U.S. Attorney Molly Gaston wrote, adding, “In short, under exceedingly difficult circumstances and under intense public scrutiny, Gates has worked earnestly to provide the government with everything it has asked of him and has fulfilled all obligations under his plea agreement.”

In a separate filing late Monday, Gates’s attorney also requested probation and community service at sentencing before U.S. District Judge Amy Berman Jackson of the District of Columbia on Dec. 17.

Gates’s attorney Thomas Green said his client also complied with three congressional subpoenas and spent more than 500 hours with federal and state prosecutors, saying “his cooperation likely represents the most extensive undertaking by any cooperating defendant” in Mueller’s or related investigations.

Gates has cared for his wife, who was diagnosed with breast cancer earlier this year, and four young children while undergoing psychological counseling, supporters wrote, and his lawyer added, “We submit that Richard Gates has accepted responsibility for his misconduct in every way possible.”

Gates included letters requesting leniency from his parents, two brothers and several other supporters, including prominent GOP consultant and former Manafort partner Charles R. Black Jr., who wrote of Gates: “When confronted with his crimes, he decided to do the right thing to make it up to his country, as much as he could. I believe that his recent suffering has restored his character and restored his high ethical standards.”

Tuesday’s government sentencing memo laid out details of what Gates told Mueller’s team and other prosecutors, filling in gaps left by Mueller’s final report in March.

The sentencing memo also recounted Gates’s key testimony at trials, most notably against Manafort.

Manafort’s defense attorneys hammered Gates’s credibility during the 2018 trial in Virginia, leaving Gates to admit to jurors that he had embezzled from Manafort, kept mistresses and doctored tax returns.

But Gates’s testimony proved crucial, and he made return appearances in court throughout this year as a witness for the government.

The Virginia jury convicted Manafort, who then pleaded guilty in another federal case in Washington.

Manafort was sentenced early this year to 7½ years in prison on both cases for conspiring to defraud the United States by concealing $30 million of what he earned while working for a Russia-backed political party in Ukraine; conspiring to tamper with witnesses; and committing bank and tax fraud to buy properties and support his lavish lifestyle.

Prosecutors charged that Manafort, with help from Gates, laundered the money over a decade through offshore accounts, and that Gates transferred more than $3 million to accounts he controlled during that time.

Mueller’s report stated that Manafort told Gates after the two were indicted that it was stupid to plead guilty because he had spoken to the president’s personal attorney and they were “going to take care of us.”

Possibly referring to that episode, prosecutors wrote to the judge that Gates faced “pressure not to cooperate with the government, including assurances of monetary assistance,” but committed to tell the truth publicly about the Trump campaign, its supporters and other powerful figures in Washington.

“Gates’ cooperation has been steadfast despite the fact that the government has asked for his assistance in high profile matters, against powerful individuals, in the midst of a particularly turbulent environment,” Gaston wrote.

Gates was back in court in August assisting Mueller’s spinoff probe of Washington lobbyists and the foreign influence industry. He testified for the government in the prosecution of Gregory B. Craig, a former top legal adviser to presidents Barack Obama and Bill Clinton. Craig was found not guilty at trial in September of lying to the Justice Department to conceal media contacts in 2012 related to his work with Manafort for the Ukrainian government.

When he took the stand in November in the trial of longtime Trump confidant Roger Stone, Gates revealed details of the Trump campaign’s keen interest in hacked, damaging emails released by the anti-secrecy group WikiLeaks that could derail Trump’s Democratic opponent, Hillary Clinton. U.S. intelligence officials had attributed that effort to Russian intelligence agencies.

Gates’s testimony included describing a phone call between Stone and Trump at a key moment in the campaign in late July 2016, in which Gates said Trump seemed to discuss WikiLeaks, calling into question the president’s assertion to Mueller’s office that he did not recall such discussions with his longtime friend.

Stone faces sentencing in February after being convicted at trial last month of tampering with a witness and lying to Congress about his efforts to learn of the hacked emails.

Gates should be commended, prosecutors wrote, “for standing up to provide information and public testimony against individuals such as Manafort, Craig, and Stone, knowing well that that they enjoy support from the upper echelons of American politics and society.”

As part of Gates’s plea, he admitted to conspiring to defraud the United States with Manafort, including keeping $3 million himself. He also pleaded guilty to lying to the FBI during an interview in which he was trying to secure a plea deal.

The charge of lying concerned Gates’ claim that a March 2013 meeting with a lobbyist and a congressman did not include a discussion of Ukraine.

Gates’s charges together carry a possible prison sentence of up to 10 years, but in a plea deal reached earlier, Gates and prosecutors agreed he would face a recommended sentence of roughly five to six years in prison, but also said at the time that each side could request less based on his cooperation. In the deal, prosecutors dropped a forfeiture demand that could have made Gates liable for up to $18 million if convicted.