President Joe Biden stumbled in the first presidential debate, against Donald Trump, on Thursday evening, fueling concerns over the presidents age.

A halting Joe Biden struggled Thursday to allay concerns he is too old for a second term in the White House in a fiery debate with Donald Trump marked by personal insults.

A bombastic Trump lashed out at his successor, calling him a failure on the economy and the world stage.

Biden looked to hit back, but his delivery was faltering as he spoke rapidly in a raspy, trailing-off voice, stumbled on his words and stared open-mouthed.

His performance, after he spent the week secluded in preparation, sparked new concern within his Democratic Party as polls show Trump is tied or ahead for the November election.

Trump and Biden, who were each the oldest president when first elected, even accused each other of being childlike as they argued over their golf swings.

Biden, 81, and Trump, 78, did not shake hands as they walked to their podiums at the CNN headquarters in Atlanta. There was no live audience and their microphones were muted as the other spoke.

Biden hit Trump with clearly rehearsed lines as he sought to remind viewers that Trump would be the first convicted felon in the White House.

“You have the morals of an alley cat,” Biden said.

Trump, a veteran of rallies and reality television, spoke loudly as he ran through a long list of complaints about Biden’s record.

“I’m friends with a lot of people. They cannot believe what happened to the United States of America. We’re no longer respected,” Trump said.

Trump sought to seize on Biden’s delivery, saying at one point, “I really don’t know what he said at the end of that sentence. I don’t think he knows what he said either.”

‘Slow start’

After the debate, Biden told reporters “I think we did well.”

The White House was clearly in damage-control mode.

Vice President Kamala Harris, in a live interview on CNN, said “Yes, there was a slow start, but it was a strong finish.”

Kate Bedingfield, a former Biden communications director, said on CNN that “it was a really disappointing” evening for the president.

California’s Democratic governor Gavin Newsom said “there shouldn’t be” panic, claiming that it was “unhelpful” and “unecessary” to turn your back on the president “because of one performance”.

A CNN poll found 67 percent of debate watchers thought Trump had won.

Republicans reacted gleefully to Biden’s poor performance.

Trump’s campaign chief, Chris LaCivita, called it “the most lopsided debate win in history”, that “added rocket fuel” for the campaign.

Vivek Ramaswarmy, the former Republican presidential hopeful, said that Trump won “hands down”, showing more energy than Biden, who he claimed would be unable to finish his term if he were to be elected president.

Democrats are set formally to name Biden as their candidate in August in Chicago, with little way to change course unless the president himself withdraws.

Personal attacks

Neither candidate laid out new policies, with most of the exchanges consisting of attacks on the other’s record.

In one of the most personal moments, Biden cited accounts that Trump had described soldiers who died in the Normandy landing as “suckers” and noted his own son Beau, who served in Iraq and later died of cancer.

Trump denied the remarks and repeatedly accused Biden of not being coherent.

On foreign policy, Trump accused Biden of not helping Israel “finish the job” against Hamas.

“He doesn’t want to do it. He’s become like a Palestinian — but they don’t like him because he’s a very bad Palestinian, he’s a weak one,” Trump said.

Trump described Biden’s withdrawal from Afghanistan as the “most embarrassing moment in the history of our country” and said it encouraged Russia to invade Ukraine.

Trump and Biden also locked horns over abortion and immigration, key issues for their respective bases.

Andrew Caballero-Reynolds and Shaun Tandon, with AFP