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The Special Counsel’s Office says it’s at “the heart” of its investigation and what went down there is of “significance” to prosecutors. Thanks to a transcript of a hearing about whether Paul Manafort violated his plea agreement, we now know that prosecutors are particularly interested in an Aug. 2, 2016 meeting between Manafort and his former Russian business partner. So what went down at that meeting and why is Robert Mueller’s team interested in it?

Kilimnik is a BFD: Andrew Weissman, one of Mueller’s top prosecutors, told the court that Konstantin Kilimnik’s activities go “very much to the heart of what the Special Counsel's Office is investigating." Kilimnik, a dual Russian and Ukrainian national and Manafort’s former business partner, was indicted alongside Manafort and charged with attempting to obstruct justice. Kilimnik and his alleged ties to Russian intelligence have been a subject of tense focus but Weissman pointed to one meeting in particular. Manafort and Kilimnik met in New York on Aug. 2, 2016 and "That meeting and what happened at that meeting is of significance to the special counsel," Weissman said.