David Axelrod, a CNN political commentator, said former special counsel Robert Mueller did not appear as sharp Wednesday as he had been in the past.
His comments came in tweets posted Wednesday as Mueller testified in front of the House Judiciary Committee.
"This is delicate to say, but Mueller, whom I deeply respect, has not publicly testified before Congress in at least six years," tweeted Axelrod, who was an adviser to former President Barack Obama. "And he does not appear as sharp as he was then."
And in another tweet, he wrote: "This is very, very painful."
He added in another tweet: "Not a commentary on the content. The report is damning. That was (re-enforced) today. He has been an exemplary public servant, as people are both sides attested, but he clearly was struggling today and that was painful."