"The [Mueller] report presents very substantial evidence that the president is guilty of high crimes and misdemeanors and we have to present — or let Mueller present those facts to the American people and then see where we go from there," he said.
"Because the administration must be held accountable and no president can be above the law."
Host Chris Wallace asked Nadler what Democrats will do if Mueller's testimony falls flat, and the House Judiciary chairman said he expects the hearing to have an impact on the electorate and plans to ask specific fact-finding questions to help enlighten the public.
"Well, we hope it won’t end up being a dud," he replied. "And we're going to ask specific questions about -- look at page 344, paragraph two, please read it. Does that describe obstruction of justice and did you find that the president did that, for example."
Nadler also said he isn't worried about Republicans asking probing questions about the investigation's origins via the Steele dossier, and claimed they'd only be wasting their time.
"It's been very clear that the Trump investigation was not predicated on the so-called dossier that they're talking about. There was nothing wrong with the FISA application. All the things they're talking about have been gone through. The inspector general found that there was nothing wrong with the other half of what they’re talking about, which is the Hillary [Clinton] investigation. He's finishing it," Nadler said.
"If they want to debate, or discuss, I should say, this irrelevancy, let them waste the time. But what's before the American people now is the conduct of this president. And what Mueller found about the conduct of this president and where we go from here."
Mueller is scheduled to appear on Capitol Hill this Wednesday to discuss the contents of his final report.