Washington DC - As the Democratic Party fights over whether Joe Biden should step aside before November's presidential election, rival Donald Trump has declined to join the pile-on.

Biden's halting debate last week against Trump fuelled concerns among voters around the president's age and ability to govern – fears that Republicans have often been eager to highlight.

Yet the Trump campaign has now pushed back against the idea of Biden (81) stepping down.

Democrats dumping their own candidate would tip them into uncertainty just months before the election – but it also carries risks for Trump, experts told AFP.

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Former Republican candidate Nikki Haley warned over the weekend that a Biden replacement would be more "vibrant," urging Republicans "to prepare and get ready for what's to come."

Trump's campaign – like top Democratic officials – has insisted that Biden is not going anywhere.

"The only way Joe Biden is dumped off the ticket is if he voluntarily decides he's not going to do it, and he's not going to make that decision," Trump campaign advisor Chris LaCivita told NBC.

Republican campaign advisor Brian Hughes said walking away from Biden would amount to Democratic "dishonesty," while Senator JD Vance – a possible Trump vice president – said doing so would be "an incredible insult" to Democratic voters.

"Trump absolutely wants Joe Biden to be his opponent – it's just like the Biden campaign always wanted Trump to be the opponent," Wendy Schiller, a political science professor at Brown University, told AFP. "They see real advantages in the weakness of the other."

Some of the names being floated as Biden replacements are "younger, vigorous, popular people in Midwest swing states," Schiller added – whom the Trump campaign couldn't blame for "inflation and the border."

By staying out of calls for Biden to step aside, Trump – who faces a slew of legal woes dogging his own campaign – is also letting bitter Democratic divisions take up the media spotlight.

"Why would the Trump campaign want to take the shovel away from Democrats who are digging their own holes right now?" Ron Bonjean, a Republican strategist, told AFP. "Every day that the spotlight is on Biden's mental sharpness is another campaign day that Trump has won."

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Trump himself has even appeared to do damage control for his Democratic rival.

"Many people are saying that after last night's performance, Joe Biden is leaving the race," Trump told a rally the day after their Thursday debate.

"The fact is, I don't really believe that," he added. "He does better in the polls than any of the Democrats they're talking about."

That was a marked turn from a few weeks ago, when Trump said in a radio interview that "if you look at [Biden] he doesn't know where he is. "

"I doubt he will even be running frankly, I just can't even imagine it."

Over the weekend, Biden met with his family at the presidential retreat at Camp David, where US media reported they discussed the 2024 race and supported Biden's plans to stay in.