Mueller Accuses Paul Manafort of Attempted Witness Tampering

“We should talk,” Mr. Manafort wrote in a WhatsApp message on Feb. 26 to one of the people at the public relations firm. “I have made clear that they worked in Europe.”

When that witness avoided him or hung up, prosecutors said, Mr. Manafort worked through an unidentified intermediary.

“Basically P wants to give him a quick summary that he says to everybody (which is true) that our friends never lobbied in the U.S., and the purpose of the program was E.U.,” the intermediary wrote in a Feb. 28 WhatsApp message, according to court documents.

Then in April, the same intermediary sent a message to another person. “My friend P is looking for ways to connect to you to pass you several messages. Can we arrange that,” the text read, according to court documents.

It is not clear exactly how the authorities learned of the communications, but prosecutors said that the witnesses provided them with copies of the messages in recent weeks.

Federal prosecutors have not identified the former European officials with whom Mr. Manafort worked. The coterie is identified in court records as the Hapsburg Group. Prosecutors said Mr. Manafort “secretly retained a group of former senior European politicians to take positions favorable to Ukraine, including by lobbying in the United States.”

In a June 2012 memorandum labeled “Eyes Only,” prosecutors said, Mr. Manafort described a plan to “assemble a small group of high-level European highly influential champions and politically credible friends” who did not have any obvious connection to the government of Ukraine.