Andrew Weissmann, who led Justice’s fraud division before being reunited with Mr. Mueller, his former FBI boss, has an operational history of going after the relatively small to snare the big.

“I would bet the indictment will be right before Thanksgiving,” said Sidney Powell, an appeals lawyer in Dallas who locked horns with Mr. Weissmann’s Justice Department task force during the Enron prosecutions of the early 2000s. “Weissmann will want to maximize the trauma to his family.”

For shock effect as well as for gathering evidence, the FBI conducted a predawn raid of Mr. Manafort’s condo in Alexandria, Virginia, in July and stayed for hours. The raid marked a ramping-up of the special counsel’s investigation into suspected Russian interference in the presidential election and collusion with the Trump campaign.