President Joe Biden sought to revive his beleaguered re-election effort on Sunday, as members of his party debated the future of his candidacy.

The president’s halting debate performance last week raised serious questions about his physical and mental capacity to run. A prime time interview with ABC on Friday fuelled further speculation about his campaign’s future.

Amid the uncertainty, Mr Biden appeared at two campaign events in Pennsylvania, a key swing state, on Sunday.

But those efforts have not stopped the president’s fellow Democrats from weighing the risks and rewards of keeping Mr Biden, 81, at the top of the ticket. On Sunday afternoon, House minority leader Hakeem Jeffries convened a meeting with ranking Democratic lawmakers that reportedly included discussion of Mr Biden’s candidacy.

Four of those on the call said they thought Biden should drop out, according to CBS, the BBC’s US news partner. Sources said at least three others expressed concern about his chances in November.

A number of top Democratic figures also voiced their stances in televised interviews over the weekend, aiming to address the question: is it riskier to stick with Mr Biden or to leave him behind?

Some say the party could be headed to defeat against Donald Trump in November if Mr Biden stays on, but others say replacing him comes with many unknowns.

Amid the fallout of Mr Biden’s disastrous debate performance, asking the president to step aside could bring some immediate relief.

Some Democrats, including avowed supporters of the president, have said as much, suggesting that concerns about his age and mental acuity had grown difficult to overcome.

The debate “rightfully raised questions among the American people about whether the president has the vigour to defeat Donald Trump”, said California Representative Adam Schiff on Sunday.

Mr Schiff stopped short of saying Biden should drop out in his interview with NBC News – a position taken publicly by five House Democrats so far.

Instead, Mr Schiff urged him to seek advice from people with “distance and objectivity” and make a decision about whether he believes he is the best candidate to run.

“Given Joe Biden’s incredible record, given Donald Trump’s terrible record, he [Biden] should be mopping the floor with Donald Trump,” Mr Schiff said. “It should not be even close and there’s only one reason it is close, and that’s the president’s age.”

Mr Biden is 81, while Trump has just turned 78. The ages of both candidates have become an increasingly contentious point among voters.

On the left, polls suggest some voters are losing faith in Mr Biden. In a Wall Street Journal poll released on Friday, 86% of Democrats said they would support Mr Biden, down from 93% in February.

A different candidate may also offer a clean slate in other areas, too. Before this wave of Democratic panic, Mr Biden drew criticism from voters on several policy fronts, including his handling of the US economy and the migrant crisis at the country’s southern border.

The president faced a threat of defection from progressive voters who oppose his response to Israel’s war in Gaza. Their resistance cost him more than 100,000 votes in Michigan – a crucial swing state – during its primary in February.

A Biden ticket “is going to drag everybody else down”, said former Ohio Representative Tim Ryan on Sunday in an interview with Fox News. “I think you’re going to see a significant amount of pressure whether it’s today or tomorrow, sometime this week, as members come back that this may be untenable for them.”

Any benefit to losing Mr Biden may be muted by the looming risks, according to some Democratic leaders.

If the president stood aside, most of what comes after remains unclear: who would replace Mr Biden, and how? And how would that candidate fare against Trump?

And in recent days, several Biden allies have stressed the pitfalls of charting a new course, arguing that Mr Biden has been a proven success.

“Biden is old,” said Vermont Senator Bernie Sanders, 82, on CBS News on Sunday. “He is not as articulate as he once was. I wish he could jump up the steps on Air Force One. He can’t. What we have got to focus on is policy – whose policies have and will benefit the vast majority of the people in this country.”

California Governor Gavin Newsom, who spent the weekend stumping for the president, said the same at a rally in Doylestown, Pennsylvania on Saturday.

“It’s the hypothetical that gets in the way of progress in terms of promoting this candidacy,” Mr Newsom said. “It’s exactly where the other party wants us to be, is having this internal fight, and I think it’s extraordinarily unhelpful.”

Mr Biden’s public supporters say replacing him may become a direct benefit to Trump’s Republicans, who can argue their opponents are engulfed in party chaos.

“We’ve got to stop talking about this,” Representative Debbie Dingell of Michigan said on CNN on Sunday. “We’ve spent a whole week. Republicans are having a great time. I mean, we need to get back to talking about Donald Trump and his performance.”

Earlier this week, former Ohio Representative Tim Ryan put forward a potential replacement: Mr Biden’s Vice-president Kamala Harris.

“I strongly believe that our best path forward is Kamala Harris,” he wrote in a op-ed for Newsweek. “Those who say that a Harris candidacy is a greater risk than the Joe Biden we saw the other night and will continue to see are not living in reality.”

Though she has demonstrated only loyal support to Mr Biden, the idea of Ms Harris, 59, stepping in for Mr Biden has gained traction in recent days.

In Adam Schiff’s Sunday morning interview, the congressman said Ms Harris could win against Trump “overwhelmingly”.

As vice-president, and a 2020 Democratic contender, supporters say she is already campaign-tested and familiar to the Democratic establishment and its fundraisers.

Ms Harris “knows the job”, said former Democratic National Committee chair Donna Brazile on ABC on Sunday. “To ask the delegates elected to the convention who are Biden-Harris supporters to bypass Kamala Harris… it would be political malpractice.”

But what makes her attractive to supporters could also be a catch: age isn’t voters’ only complaint against Biden and the administration’s baggage surrounding policy choices could extend to Ms Harris.