Biden falters in high-stakes debate, Trump spews falsehoods

Biden and Trump are navigating different expectations heading into the debate -- though Republicans have largely set the standards for each.

Polls show that voters share concerns about Biden's age (81 years old) and fitness for office, and Republicans have for years cast the president as a dithering man. Showing vitality, as he did during this year's State of the Union, and nimbly mixing it up with Trump, could help alleviate those worries, Democrats told ABC News.

Trump, meanwhile, has been working overtime to set his own expectations. He's repeatedly demeaned CNN -- the host -- to suggest he'll be debating behind enemy lines. And he's emphasized his unfounded claims that Biden will be on some kind of drug to enhance his performance, seemingly to undercut the prospect of a good performance by the president. Some Republicans have also been highlighting Biden's extensive resume of running races and debating.

Still, Trump's allies are setting high expectations for him, with senior adviser Jason Miller telling ABC News that Trump has demonstrated "elite stamina."

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Trump arrived in Atlanta just before 5:30 p.m. As he exited the plane, he raised his fist and clapped his hands.

He went straight into his motorcade without approaching or greeting nearly 200 supporters who gathered to welcome him.

Accompanying him were his advisers Susie Wiles, Steven Cheung, James Blair, Jason Miller, Chris LaCivita, and Corey Lewandowski. The only lawmaker on the plane with him was Republican Rep. Matt Gaetz of Florida.

Biden stepped off Air Force One in Georgia about 3:15 p.m. to greet a group of supporters on the tarmac applauding his arrival. The president was donning his signature aviators and a navy-blue suit.

He spent several moments shaking hands with Atlanta Mayor Andre Dickens, former mayor Keisha Lance Bottoms, Stacey Abrams and Jason Carter, Jimmy Carter's grandson.

As he made his way to CNN's studio, Biden made an unexpected stop to shake hands with a group of cheering supporters. The group held "Dark Brandon" cardboard cutouts and chanted "Let's go, Joe!" and "Four More Years!"

Biden moved down the line to shake hands and meet people for nearly 10 minutes.

-ABC News' Molly Nagle

As Biden and Trump prepare to square off in their first political debate in four years, historians and experts contend the matchup may have a small but crucial impact on the election.

Aaron Kall, director of debate for the University of Michigan's Debate Program, told ABC News the majority of those who tune in are likely already locked into a preferred candidate.

"Nothing that occurs during the 90-minute debate is going to change or influence who they're going to vote for," he said.
However, Kall and other experts ABC News spoke with said there is still a smaller group of undecided voters who do tune in and can be swayed by the performances.

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Do presidential debates still matter?

Candidates, such as Donald Trump and President Joe Biden in 2024, are vying for smaller groups of undecided voters who watch the debates, experts say.

With the last two presidential elections decided by just tens of thousands of votes in a few states -- many cast by independent voters -- candidates' debate strategies have become laser-focused on courting that group, according to Julien Labarre, administrator of the University of California Santa Barbara's Center of Information Technology & Society.

"What we see is people who were not thinking of going to vote being turned into voters," he told ABC News. "Spurring people into participation, we do see that kind of effect."

-ABC News' Ivan Pereira