Two prosecutors who worked on the investigation and prosecution of Paul Manafort are returning to their former divisions at the Justice Department, although at least one will remain engaged in matters under Mr. Mueller’s purview. A third relatively junior prosecutor left in July. Mr. Manafort, Mr. Trump’s former campaign chairman who was convicted of multiple counts of fraud in August and then pleaded guilty to conspiracy charges, is cooperating with special counsel’s office.

Mr. Mueller has referred several investigations and prosecutions to local offices of United States attorneys, either because they were outside his mandate or because the cases could drag on for years. The most recent court filings indicate the United States attorney for the District of Columbia, for instance, is now taking the lead in prosecuting the Russian individuals and companies charged in the scheme in which Mr. Pinedo became ensnared. Mr. Atkinson hinted to Judge Friedrich that the special counsel’s office might have turned over some leads provided by Mr. Pinedo to federal prosecutors with “a wider bandwidth” to investigate them.

Though Mr. Pinedo understood he was acting as a middleman for foreigners, Mr. Lessem argued in court papers that “never in his wildest dreams could he have foreseen that providing bank account information to set up PayPal accounts could be used to interfere with a presidential election.”

He told the judge that because of the investigation’s high profile, his client was a target of threats and harassment, a punishment in itself. Mr. Pinedo said some people have accused him of being a Russian agent while others have delivered veiled threats of retaliation for his testimony against Russian operatives. “Just leaving my home to run errands is extremely stressful,” he told the judge.

Judge Friedrich said that while Mr. Pinedo deserved credit for his cooperation and sympathy for the harassment he and his family had endured, he had engaged in identify fraud on a large scale for a period of three years. “You committed a serious crime,” she said, “with real consequences.”

According to court papers, Mr. Pinedo earned $40,000 to $95,000 enabling the Russians and others to bypass safeguards and gain access to online financial networks.