Attorney General William Barr is reportedly anxious about former special counsel Robert Mueller's hearing on Wednesday.

"I heard from a source familiar with Attorney General Barr's thinking that he is nervous about being attacked tomorrow," MSNBC host Nicolle Wallace said during an interview with former FBI Director James Comey.

She then asked Comey what kind of exposure Barr might have during the testimony.

"I don't think he will be attacked by the witness or witnesses. I think he may be attacked by Democrats, fairly, in my view for misrepresenting what was in Director Mueller's report and how he handled the entire thing and the way he has slimed the FBI since," Comey said. "Frankly, I hope there is not a lot of that. Because this is a chance for the American people to learn more about what the special counsel found and the fewer attacks and the more questions the better served the American people will be."

Mueller, who reluctantly agreed to testify publicly only after he was subpoenaed, will appear with longtime counsel Aaron Zebley before the House Judiciary and Intelligence committees starting Wednesday morning.

Mueller’s report, released by the Justice Department with redactions in April, concluded that Russia interfered in the 2016 election but did not establish that any members of the Trump campaign criminally conspired with the Russians in these efforts. Mueller did not reach a conclusion on obstruction of justice, citing Justice Department policy against indicting a sitting president, but Barr and then-Deputy Attorney General Rod Rosenstein concluded there was insufficient evidence for such a crime in the summary the Justice Department released preceding the report.

Democrats argue Barr misled the public and that by laying out 10 instances of possible obstruction in his report, Mueller left it up to Congress to decide whether President Trump obstructed justice. Trump and his allies claim the president has been vindicated.

Barr told reporters Tuesday that Mueller asked the Justice Department for guidance on what he can testify "within the boundaries" of his 448-page report, which irked Democrats.