STORY: :: Analysts say mental fitness will be a key focus in Biden and Trump's upcoming debate

:: Kathleen Hall Jamieson, Professor of Communication, University of Pennsylvania

"This year, because of the age of both, there is a need, even if you think you know a lot about both of the candidates, and you're more likely to this year for you to be able to say, are they mentally acute enough to be president of the United States and mentally stable enough to be president of the United States? And those are different assessments. A question about Trump is stability. The question about Biden is acuity. Although you could make the argument that the question should be about both for both."

:: Alan Schroeder, Professor Emeritus of Journalism, Northeastern University

"So in the case of Joe Biden, you know, I think it's been interesting that Trump and his surrogates have really downplayed Biden's abilities and, and his even his mental acuity at this point, because that's really a gift to Biden. You know, it just means that if he exceeds that level of performance, that he looks better than people expected him to."

:: Philippe Reines, Democratic U.S. Political Consultant

"And one way to really show that that's just not true is to show the "full Joe Biden." I mean, the people I know who worked with Joe Biden in the white House to see him, if not daily, then regularly, that I hear about. I mean, he can be, you know, rough. He can be, you know, pretty strong on people. He could be pretty strong on circumstances. He can be funny. He can be all sorts of things that we don't see him when he's at a teleprompter looking into them and squinting. And I think this is an opportunity to show that."

The debate will be the earliest presidential debate in modern U.S. history and a critical event for both candidates.

It will include two commercial breaks, no props and muted microphones when the other candidate is speaking to head off a repeat of their often raucous 2020 debates.

Biden, 81, and former president Trump, 78, are neck-and-neck in national opinion polls, with a considerable slice of the electorate still undecided five months before the Nov. 5 vote.