from the opinion piece written by Toobin

Not officially, of course. John G. Roberts, Jr., retains the title and the middle seat on the Supreme Court bench. But the Chief Justice has just one essential power that differentiates his role from that of the other Justices. The Chief has the right to assign the court's opinions when he is in the majority. When the Chief Justice is in the minority, though, the assignment power goes to the senior Associate Justice who is in the majority.