WASHINGTON — President Donald Trump’s former lawyer, Michael Cohen, was in touch as far back as 2015 with a Russian who offered “political synergy” with the Trump election campaign, the federal special counsel said Friday in a court filing.

Filings by prosecutors from both New York and the Trump-Russia special counsel’s office laid out for the first time details of the cooperation of Cohen, a vital witness who once said he’d “take a bullet” for the president but who in recent months has become a prime antagonist and pledged to come clean with the government.

Federal prosecutors said Friday that Cohen deserves a substantial prison sentence despite his cooperation with investigators. He is set to be sentenced next week.

Among the factors laid out by prosecutors in seeking a prison term of about four years for Cohen, they highlighted Cohen’s failure to disclose to the Internal Revenue Service more than $2.4 million he earned from 22 taxi medallions he operated in Chicago between 2012 and 2016. The medallions are managed by Chicago Medallion Management, a company owned by the family of Semyon Shtayner and his wife Yasya, Ukrainian immigrants who live in Trump properties in New York City and Florida.

According to the sentencing memo, Cohen spent hours with prosecutors detailing his intimate involvement in an array of episodes, including some that directly touch the president, that are at the center of investigations into campaign finance violations and potential collusion between the Trump campaign and the Kremlin.

In one of the filings, Mueller details how Cohen spoke to a Russian who “claimed to be a ‘trusted person’ in the Russian Federation who could offer the campaign ‘political synergy’ and ‘synergy on a government level.'”

The filing says the meeting never happened.

Cohen also discussed a Moscow real estate deal that could have netted Trump’s business hundreds of millions of dollars and conversations with a Russian intermediary who proposed a meeting between Trump and Russian President Vladimir Putin as well as offering synergy with the campaign, prosecutors said.

Cohen, dubbed Trump’s “legal fixer” in the past, also described his work in conjunction with Trump in orchestrating hush money payments to two women — a porn star and a Playboy model — who said they had sex with Trump a decade earlier. Prosecutors in New York, where Cohen pleaded guilty in August in connection with those payments, said the lawyer “acted in coordination and at the direction” of Trump.

Despite such specific allegations of Trump’s actions, the president quickly tweeted after news of the filings: “Totally clears the President. Thank you!”

In addition, the filings reveal that Cohen told prosecutors he and Trump discussed a potential meeting with Putin on the sidelines of the U.N. General Assembly in 2015, shortly after Trump announced his candidacy for president.

In a footnote, special counsel Robert Mueller’s team writes that Cohen conferred with Trump “about contacting the Russia government before reaching out to gauge Russia’s interest in such a meeting,” though it never took place.

In an additional filing Friday evening, prosecutors said former Trump campaign chairman Paul Manafort lied to them about his contacts with a Russian associate and Trump administration officials.

Manafort, who has pleaded guilty to several counts, violated his plea agreement by then telling “multiple discernible lies” to prosecutors, they said.

Prosecutors in Cohen’s case said that even though he cooperated in their investigation into the hush money payments to women he nonetheless deserved to spend time in prison.

“Cohen did provide information to law enforcement, including information that assisted the Special Counsel’s Office,” they said. “But Cohen’s description of those efforts is overstated in some respects and incomplete in others.”

In meetings with Mueller’s team, Cohen “provided information about his own contacts with Russian interests during the campaign and discussions with others in the course of making those contacts,” the court documents said.

Cohen provided prosecutors with a “detailed account” of his involvement, along with the involvement of others, in efforts during the 2016 presidential campaign to complete a deal to build a Trump Tower Moscow, the documents said. He also provided information about attempts by Russian nationals to reach Trump’s campaign, they said.

However, in the crimes to which he pleaded guilty in August, he was motivated “by personal greed and repeatedly used his power and influence for deceptive ends.”

Prosecutors said the court’s Probation Department estimated that federal sentencing guidelines call for Cohen to serve at least four years in prison. They said that “reflects Cohen’s extensive, deliberate and serious criminal conduct.”

Prosecutors say Cohen “already enjoyed a privileged life,” and that “his desire for even greater wealth and influence precipitated an extensive course of criminal conduct.”

Associated Press writers Larry Neumeister in New York and Michael Balsamo in Washington contributed to this report.