Five takeaways of Biden-Trump debate

President Joe Biden and Republican challenger Donald Trump squared off Thursday in a debate watched by millions, and what voters saw may have sparked more questions than answers.

Here are five takeaways from the Atlanta showdown.

- Dems, we have a problem -

Biden -- diagnosed with a cold, according to his campaign -- looked all of his 81 years onstage, speaking in a halting, hoarse voice and missing key opportunities to forcefully and coherently push back against Trump.

While the veteran Democrat showed occasional spark, he mostly appeared lackluster. The post-debate analysis came in quickly -- and it was devastating.

"It was an unmitigated disaster," University of Virginia political science professor Larry Sabato told AFP.

"This debate is a problem," added Princeton University professor Julian Zelizer, saying Biden's supporters "are going to be extremely concerned how this unfolded."

Trump at times looked more authoritative and energetic, although he unleashed a barrage of falsehoods about Biden's presidency, election fraud and abortion policy.

- A more disciplined Trump -

Of the two candidates it was Trump who may have surprised viewers, by showing a more restrained, civil side to his normal political bulldozing. Host CNN turned the microphones off unless a candidate was asked a question, a move experts say benefited the challenger.

When Biden railed against Trump, for example, for having "encouraged" rioters to storm the US Capitol in early 2021, Trump largely held his tongue, looking down or shaking his head.

And when it was his turn to speak, he pounced.

"Trump's somewhat tempered and authoritative demeanor -- at least for him -- masked a number of mistruths he made throughout the night and helped him appeal to swing voters on top polling issues like the economy and the border," Ashley Koning, director of the Rutgers Eagleton Center for Public Interest Polling, told AFP.

- It's personal -

The debate, which began without a handshake, left no doubt these men do not like one another. From Biden's blasting his rival as "a convicted felon" to Trump musing that "I don't think (Biden) knows what he said," the personal animus was glaring.

"You have the morals of an alley cat," Biden hissed after laying out Trump's various legal woes and verdicts against him.

"You're the sucker, you're the loser," Biden said.

Trump punched back, saying "everything he does is a lie."

"He's the worst president in the history of our country," Trump fumed.

- Less chaos, less accountability -

The helter-skelter tumult of their first 2020 debate, in which then-president Trump ran roughshod over Biden and the debate moderators, was but a memory Thursday night, as CNN's strategy to avoid a shouting match worked.

"I think the rules may have aided Trump because they prevented him from yelling over Biden's answers," said Robert Rowland, a communications professor at Kansas University.

With no studio audience cheering or jeering, both candidates had greater opportunities to focus on the issues.

And with CNN moderators failing to offer real-time fact checks during the debate, Trump and to a lesser degree Biden were unrestrained in making misleading or false statements on a variety of topics, from immigration and crime to the economy.

- Ominous tone -

Trump's couched response to a key question near the debate's end offered a concerning look into the post-election future.

Moderators asked Trump three times whether the Republican would accept the results of the vote before he finally addressed the question directly, saying "if it's a fair and legal and good election, absolutely."

But in the same breath he repeated his baseless claims about 2020 vote rigging or interference, saying "the fraud and everything else was ridiculous."

Biden suggested even Trump's conditional response should not be trusted. "I doubt that you'll accept it because you're such a whiner," Biden said.