Democratic Rep. Ted Lieu floated a theory related to Robert Mueller's testimony during an interview on CNN Thursday evening.

Mueller testified in front of the House Judiciary Committee and the House Intelligence Committee about his two-year long investigation the day before. Lieu's questioning of the special counsel offered one of the biggest gains for Democrats, but Mueller later walked it back.

“The reason again that you did not indict Donald Trump is because of [Office of Legal Counsel] opinion stating that you cannot indict a sitting president, correct?” Lieu asked Mueller during the hearing, which he said was a "correct" statement.

The affirmative statement would've been a big admission by the special counsel, essentially confirming that the president would've been indicted had he not been the sitting president.

But, Mueller clarified his affirmation to Lieu's question during his opening remarks of his second testimony.

“I want to go back to one thing that was said this morning by Mr. Lieu, who said, and I quote, ‘you didn’t charge the president because of the OLC opinion,'” the special counsel began.

“That is not the correct way to say it,” he added, “as we say in the report, and as I said in the opening, we did not reach a determination as to whether the president committed a crime.”

CNN's Wolf Blitzer asked Lieu about Mueller's correction Thursday.

"This is what’s so odd about that exchange," Lieu began. "Special counsel Robert Mueller agreed that the OLC opinion prevented a sitting president from being indicted. And then the Republican member after me asked him a series of questions to try to get him to walk it back. He did not do that. And then it doesn’t until there was a recess with the Intel committee that he started to walk some of that back. I don’t know who got to him, I don't know who talked to him, but that was very odd."

"What are you suggesting? Because he said he misspoke. He didn’t understand, or whatever it was. That’s why he wanted to clarify and walk back his response to your question. Are you saying he only did that because of pressure from someone?" Blitzer asked.

"I don’t know. But he clearly answered the way he answered to me, and then he had numerous times to walk that back by the next Republican member who asked him a series of questions on the exact same issue trying to get him to walk it back," the congressman concluded.