The indictment of Paul Manafort and Rick Gates last year was ultimately accepted, if not welcomed, by allies of Donald Trump. Yes, the former Trump campaign chairman and his deputy had been charged with a dozen counts, including the ominous-sounding “conspiracy against the United States”—hardly a good look for two men who were instrumental in the president’s election. But the “conspiracy” that Robert Mueller had uncovered—an effort to launder money from consulting work in Ukraine, tax-free—appeared not to have anything to do with Trump, or Russia, or any collusion between the two. When Gates, buried in legal bills and concerned about his family, pleaded guilty in February to financial fraud and lying to investigators, in exchange for a reduced sentence and multiple dropped charges, it was believed that he had cut a deal to testify against Manafort.

According to a new CNN report, however, Mueller was more interested in what Gates could share about the Trump campaign’s ties to Russia than strengthening the case against Manafort. That revelation—confirmed to CNN by a source familiar with the investigation—first came into focus earlier this week when a court document released by Mueller alleged that Gates had repeated contacts with an individual with ties to Russian intelligence during the final stretch of the presidential campaign. Between September and October 2016, Gates was in frequent conversations with this person, which the Mueller team characterized as “pertinent to the investigation” in the filing. The document also says that Gates told an associate that the individual, identified as “Person A,” “was a former Russian Intelligence Officer with the G.R.U.” The New York Times reported that “Person A” is Konstantin Kilimnik, who worked with Manafort in Ukraine and who the F.B.I. believed to have active ties to the Kremlin. (Kilimnik, a Russian army-trained linguist who has previously said he has a background in Russian intelligence, has more recently claimed to have “no relation to the Russian or any other intelligence service.”) The filing was a sentencing memorandum for Russian lawyer Alex van der Zwaan, who pleaded guilty to lying to the F.B.I. earlier this year about his contacts with Manafort and Gates. (Manafort has denied any wrongdoing and pleaded not guilty in the Mueller case.)

Gates’s testimony could prove crucial as Mueller seeks to determine what role, if any, the Trump campaign played in Russian election meddling. Gates, who served as Manafort’s No. 2 and worked on Trump’s inaugural committee after the election, was a key member of the Trump campaign at critical points. “Was he in the strategy meetings? No. But he was an implementer,” one person said of Gates to CNN. This person added that if there was any coordination between the Trump campaign and the Russians, “He would be the kind of person who would probably know that.” Gates was a major player on the campaign at the time of Donald Trump Jr.’s infamous June 2016 Trump Tower meeting with Russian lawyer Natalia Veselnitskaya, as well as during the Republican National Convention, where the Trump campaign reportedly altered the language in the G.O.P. platform to be more favorable toward Russian interests.

That latter episode has reportedly piqued the special counsel’s interest recently. Citing two sources familiar with the probe, Reuters reported Thursday that Mueller has been asking witnesses about why language adverse to Russian interests was removed from a section about Ukraine in the Republican Party platform. Specifically, members of the Trump campaign are said to have been instrumental in stripping language that said the United States should provide “lethal defensive weapons” to Ukraine. The Trump administration has since approved new weapons sales to Ukraine, and recently expelled 60 Russian diplomats from the U.S. in retaliation for the Skripal poisoning in Britain.

Legal experts I’ve spoken to have pointed to Mueller’s tactics as evidence that the special counsel is following the same mafia-takedown tactics he used in the 1990s to prosecute John Gotti: targeting lower-level members of Trump’s inner circle, cutting deals, and then moving up the food chain. “With every benefit comes a price,” and that price is “to cooperate and provide what the prosecutors call ‘substantial assistance’ to the federal investigation,” Renato Mariotti, a former Illinois federal prosecutor, told me recently. “What that means is cooperation that could result in charges against somebody that is important to the investigation.” For months, the conventional wisdom was that the next man up the food chain was Manafort. With CNN’s reporting, however, it seems increasingly likely that the big fish could be Trump.

“Draw your own conclusions,” Trump’s former lead attorney on the Russia case, John Dowd, told Politico when asked about that possibility, shortly before he resigned last week after clashing with the president. “I’m not concerned.”