Barr won't let Trump supporters give up 'deep state' conspiracy theories: MSNBC anchor
President Trump, at a campaign rally, Aug. 1, 2019, in Cincinnati. AP/John Minchillo

MSNBC's Andrea Mitchell says the Justice Department inspector general's testimony doesn't matter, because the attorney general had already undercut his credibility.

Michael Horowitz, the department's inspector general, told the Senate Judiciary Committee about the findings in his report on the origins of the Russia probe, but Mitchell said Attorney General William Barr made that testimony unnecessary.

"At this stage, everybody is locked into their positions," Mitchell said. "You're never going to persuade the partisans who support the president's conspiracy theories. You see them at the rallies and out on the campaign trail."

Horowitz found no evidence that the FBI was motivated by partisan interests to investigate ties between the Trump campaign and Russia, which contradicted the president's claims, but Barr has said he disagrees.

"You're never going to persuade them that Mr. Horowitz was correct and there was no poisonous, deep state conspiracy here," Mitchell said, "especially when you have attorney general fueling it with the continuing investigation by the assistant U.S. Attorney from Connecticut, (John) Durham."