Jerry Nadler, the Democratic chairman of the House Judiciary Committee, has invited Mueller to appear before the panel "no later than May 23" to testify about the findings of his 22-month-long investigation.
Trump said on Friday he would decide within a week or so whether to assert executive privilege to block McGahn from testifying before Congress.
Trump's reversal on Mueller was sudden. Someone, perhaps a member of Mr. Barr's staff, should inform the attorney general that when the person in charge signs a letter, regardless of who drafted it, it becomes that person's letter. William Barr has said he has no objection to Mueller testifying. Not only because Harris asked questions with unflinching precision but because she left Barr with no choice but to obfuscate about whether or not President Donald Trump or other White House officials "asked or suggested" Barr open an investigation into anyone.
Mueller also found 10 "episodes" of potential obstruction of justice but ultimately concluded that it was not his decision to determine whether Trump broke the law.More news: Pelosi accuses Barr of lying in Congress
Barr had objected to Democrats' plans to use outside attorneys to conduct part of the questioning; Democrats say this has been done before, notably in the Watergate hearings. But in his March 24 summary, Barr stated that Mueller's investigation found no conspiracy between Trump's campaign and Russian Federation, and that he, along with then-Deputy Attorney General Rod Rosenstein, concluded that "the evidence developed during the Special Counsel's investigation is not sufficient to establish that the President committed an obstruction-of-justice offense".
The House Judiciary Committee has been seeking to hear from Mueller amid disagreements about whether Barr mischaracterized the special counsel's report in his congressional testimony and statements.
The Justice Department said last week that it was "unable" to provide the investigative files Mueller compiled during his investigation, due to a "compelling need to protect the autonomy and effectiveness of its investigations".
"If the department persists in its baseless refusal to comply with a validly issued subpoena, the committee will move to contempt proceedings and seek further legal recourse", Nadler wrote.
Then, on March 24, Democrats and the media learned not only that there was no collusion case (which was no surprise) but that Mueller had been derelict, failing to render a judgment on the only question he was arguably needed to resolve: Was there enough evidence to charge obstruction? Clearly, it is not to do the work we sent them there to do for the people of our country but instead to hold on to their precious jobs for another term. McGahn also said the president later asked him to deny having made that request.