Special counsel Robert Mueller filed a new indictment Friday against former Trump campaign chairman Paul Manafort, charging him and a Russian associate with obstruction of justice for allegedly trying to tamper with witnesses. The grand jury action against Manafort and Konstantin Kilimnik, who law enforcement officials have said is associated with Russian intelligence, marks the latest tightening of the screws by Mueller. Prosecutors previously raised the witness tampering claims in a motion to revoke Manafort's bail.