Senate Judiciary Chairman Lindsey Graham (R-S.C.) tweeted Sunday that he will grant Democrats' request to call former special counsel Robert Mueller to testify before his committee.The big picture: The announcement comes on the heels of Mueller publishing an op-ed in the Washington Post that defended the Russia investigation and conviction of Roger Stone, whose sentence was commuted by President Trump on Friday.Mueller testified to the House Intelligence and Judiciary committees in July last year, following the release of his 448-page report to Congress. The 75-year-old former FBI director was criticized for appearing confused and unfamiliar with some aspects of the report.Graham, who is leading one of several investigations into the origins of the Russia probe and alleged misconduct by the FBI, has previously said that he's "done with the Mueller report" and wants to move on.What he's saying: "Apparently Mr. Mueller is willing - and also capable - of defending the Mueller investigation through an oped in the Washington Post." Graham tweeted."Democrats on the Senate Judiciary Committee have previously requested Mr. Mueller appear before the Senate Judiciary Committee to testify about his investigation." Go deeper: Robert Mueller speaks out on Roger Stone commutation