President Donald Trump on Thursday urged lawmakers, one in particular, Sen. Lindsey Graham, R-SC, to request former President Barack Obama’s testimony before Congress to answer key questions about his administration’s ‘unmasking’ of Lt. Gen. Michael Flynn used to target Trump.

“If I were a Senator or Congressman, the first person I would call to testify about the biggest political crime and scandal in the history of the USA by FAR, is former President Obama. He knew EVERYTHING,” Trump wrote on Twitter.

He added, “Do it Lindsey Graham, just do it. No more Mr. Nice Guy. No more talk!”

In a statement Wednesday, Graham said that he ‘appreciated’ the acting Director of National Intelligence’s action to release the list of names of Obama administration officials who were involved in the unmaskings.

 “The unmasking of General Flynn by the Obama Administration regarding conversations during the presidential transition are deeply troubling and smell of politics, not national security,” Graham said, adding that Congress must act as a next step to “perform oversight of these unmasking requests to ensure the process was used for legitimate national security concerns, not reprisals or political curiosity.”

He continued, “I specifically want to know how many unmasking requests were made, if any, beyond General Flynn regarding members of the Trump campaign team, family, or associates.”