NEW YORK — US President Joe Biden has assured Democrat donors that he can still win November's presidential election against Donald Trump, after a poor debate performance fuelled concern about his candidacy.

The president, 81, attended a series of fundraising events in New York and New Jersey on Saturday, defending his performance in CNN's Presidential Debate. Speaking at one event, Biden admitted, "I didn’t have a great night, but neither did Trump."

"I promise you we're going to win this election," he said.

Biden's debate performance was marked by hard-to-follow and shaky answers, raising fresh fears among some Democrats over whether he is the right candidate to contest this high-stakes election. Former Democratic House speaker Nancy Pelosi said Biden's debate performance “wasn’t great,” while his former communications director, Kate Bedingfield, called it “really disappointing.”

The president said he understood the concern but pledged to fight harder. New Jersey's Democratic governor Phil Murphy attended the fundraiser alongside Biden and the First Lady, telling Biden that "we are all with you 1,000%."

The Biden campaign accepted that the debate had not gone as they had hoped, but said he would not step aside for another nominee. Campaign chairwoman Jennifer O'Malley Dillon said on Saturday that internal post-debate polling showed "voters' opinions were not changed."

"It will not be the first time that overblown media narratives have driven temporary dips in the polls," she said.

Former President Barack Obama, a close friend of Biden, said on social media that "bad debate nights happen." "This election is still a choice between someone who fought for ordinary folks his entire life and someone who only cares about himself," Obama wrote.

Hours after the debate, Trump told his supporters that he considered the debate a "big victory" for his campaign. "Joe Biden's problem is not his age," the 78-year-old Trump said. "It's his competence. He's grossly incompetent."

Biden's performance was not only criticised by those in politics. A prominent editorial in the New York Times described his determination to run again as a "reckless gamble," urging him to do some soul-searching this weekend. It said Democrats should "acknowledge that Biden can’t continue his race, and create a process to select someone more capable to stand in his place."

Voters across the United States have also expressed concerns over voting for either candidate following Thursday's debate. Long-time Democrat Lori Gregory told the BBC that she "could not handle" watching the debate and asked, "is this the best our country can do?" Republican Crystal Myers-Barber said it was "painful to watch," but added that she thought "Trump came across very level-headed and presidential and Biden came across very weak."

Democrat Shana Ziolko said she was "frustrated" watching the debate and thought there was no clear winner. A post-debate poll by liberal pollster Data for Progress found that 62% of likely voters who watched or read about the debate found Trump won. Only 30% of those polled said Biden won the debate.

Until further polling is conducted, fundraising could be another indication of continued enthusiasm for Biden's candidacy. In a memo, chairwoman Jennifer O'Malley Dillon said the campaign had raised more than $27m from the Thursday debate to Friday evening. "Following Thursday night’s debate, the beltway class is counting Joe Biden out. The data in the battleground states, though, tells a different story," she said.

"This election was incredibly close before Thursday, and by every metric we’ve seen since, it remains just as close," she added. — BBC