WASHINGTON — The trial of Paul Manafort was not about election conspiracy or presidential obstruction of justice. Michael D. Cohen pleaded guilty to crimes that had nothing to do with Russia’s campaign to sabotage the 2016 presidential race.
Yet the deepening legal peril for both men could have significant implications for the current investigation by the special counsel, Robert S. Mueller III.
The cases of both men are, at the moment, tangential to the central questions of Mr. Mueller’s inquiry: whether President Trump and his associates conspired with Russia’s election interference, and whether the president tried to obstruct the Justice Department’s investigation into the matter. But neither Mr. Manafort nor Mr. Cohen are believed to be cooperating with the special counsel — situations that could change now that they face years in prison.
Whether either man has anything of value to offer Mr. Mueller’s investigators is another question, and experts pointed out that the legal proceedings have dealt significant damage to the credibility of both. The team for Mr. Cohen, the president’s former lawyer, at least, has signaled a willingness to provide information to the special counsel in exchange for some kind of leniency.
“Cohen has done everything but shout from the rooftops that he wants to cooperate,” said Ross Garber, a criminal defense lawyer and adjunct professor at Tulane Law School. “I expect the government is interested in what he has to say, and then can evaluate whether there is any value to it.”
Mr. Cohen’s plea agreement, formalized on Tuesday afternoon in a Lower Manhattan courtroom, does not require that he cooperate with federal investigators in New York who have been scrutinizing payments to two women to secure their silence before the 2016 election about affairs that they say they had with Mr. Trump. But even though Mr. Cohen has pleaded guilty in New York, legal experts say, Mr. Mueller can still call him to testify before the grand jury in Washington hearing evidence about the Russia investigation.
As for Mr. Manafort, the former chairman of the Trump campaign, Mr. Mueller’s prosecutors built their case on two timeless and prosaic matters: greed and theft. They sketched a portrait of a man who raked in millions in foreign lobbying and tried every means he could to hide the income in offshore bank accounts to evade federal taxes.
What he did not pay in taxes, the prosecutors argued, he spent on cars and expensive clothes, even a $15,000 coat made of ostrich skin.
That the charges against Mr. Manafort had nothing to do with Russian interference in the election opened Mr. Mueller’s team to a barrage of attacks by Mr. Trump and his allies that the special counsel had embarked on a crusade to discredit the administration.
But the fact that a jury returned a guilty verdict on eight counts bolsters the credibility of the special counsel’s pursuit of Mr. Manafort’s financial crimes. Mr. Mueller was directed to investigate Moscow’s interference, possible coordination by Trump associates and any other potential crimes he discovered along the way.
“The verdict highlights that the prosecutors are not engaged in a witch hunt. They aren’t engaged in fabricating evidence of following shadows,” said Jimmy Gurulé, a professor at Notre Dame Law School. “It goes to the competency of the investigation.”
Mr. Trump clearly believes otherwise, and on Tuesday, he tried to use the Manafort verdict as evidence of an overzealous team of biased prosecutors.
“It doesn’t involve me,” he said on the tarmac as he deplaned Air Force One in Charleston, W.Va., for a rally. “This has nothing to do with Russian collusion. This started as Russian collusion.”
“It’s a disgrace,” he said.
Of all of President Trump’s top advisers during the campaign, Mr. Manafort’s connections to Russian businessmen and Russia-aligned politicians ran the deepest. He earned tens of millions of dollars over several years in Ukraine bolstering the political fortunes of Viktor F. Yanukovych, the president at the time and an ally of President Vladimir V. Putin of Russia. Mr. Manafort did business with Oleg V. Deripaska, a Russian oligarch, before a dispute over money ended the relationship.
One of Mr. Manafort’s close business associates in Kiev was Konstantin V. Kilimnik, a Russian whom Mr. Mueller’s prosecutors have said had active ties to Russian intelligence — including in 2016, when he was in contact with Mr. Manafort in the months before the presidential election.
Mr. Manafort is set to face another trial in Washington next month, during which his relationship with Mr. Kilimnik is expected to be part of the government’s case. In indictments in that case, prosecutors have argued that Mr. Kilimnik and Mr. Manafort tried to influence the testimony of two witnesses.
Mr. Manafort’s conviction on Tuesday could, in theory, change his legal strategy before the next trial. Where Mr. Mueller and his team go next is an even bigger unknown. The special counsel’s office has made a practice of keeping government officials, legal experts and journalists guessing about the investigation’s strategy.
Whether or not Mr. Cohen or Mr. Manafort end up directly aiding the Mueller investigation, the twin courtroom dramas on Tuesday have — at the least — added fuel to the argument that a president who rose to power pledging to “drain the swamp” surrounded himself with a coterie of unscrupulous advisers.
“This doesn’t reflect positively on the president,” Mr. Gurulé said, understatedly. “We’re talking about long-term criminal activity.