Joe Biden accidentally referred to Vice President Kamala Harris as “Vice President Trump” as he answered his first question at a closely watched, high-stakes press conference while under pressure from Democratic officials to end his re-election campaign against his Republican rival.

Biden responded to several questions about his fitness for office and his viability as a candidate against Donald Trump after the 81-year-old president appeared to unravel during a presidential debate against him two weeks ago.

Biden arrived on stage on Thursday facing a mandate from Democratic officials and voters to prove he is up to the task of campaigning against Trump for the next four months, let alone serving another demanding four-year term in the White House.

Follow latest updates on Biden as pressure grows on him to stand aside

“Look, I wouldn’t have picked Vice President Trump, to be vice president, if she’s not qualified to be president.” he said, before correcting himself.

Asked later whether he would step down if polling data showed that Harris would fare better against Trump, he whispered: “No one’s saying that.”

Biden, who frequently cleared his throat and garbled his responses, faced several urgent questions from reporters about his viability as he navigated relatively complex statements about foreign policy and US posture.

The president insisted he is staying in the race and remained optimistic about his chances and his political future, pointing to his record in office and renewed global alliances during this week’s NATO summit.

“The fact is,” Biden said, “I’m the most qualified person to beat Trump. I beat him once, I’ll beat him again.”

“Where’s Trump been,” he said at one point. “Riding around on his golf cart, filling out a scorecard before he hits the ball?”

Asked whether he can reassure Americans that he won’t have “more bad nights” like his admittedly “stupid mistake” of a performance against Trump at their first 2024 debate, Biden said there is “no indication” that his work is “slowing down.”

“Am I getting the job done? Can you name me somebody who has gotten more major pieces of legislation passed in three and a half years?” he said.

“I created 2,000 jobs just last week,” he added. “If I slow down and can’t get the job done, that’s a sign that I shouldn’t be doing it. But there’s no indication of that yet. None.”

He said it would be “smarter for me to pace myself more.”

“My schedule has been full bore,” he said. “I love my staff, but they add things.”

He joked that he is “catching hell from my wife” for his demanding schedule.

“I’m not in this for my legacy,” he said. “I’m in this to complete the job I started.”

Asked whether he would take another neurological exam before November’s election, he said: “I think it’s important that I, if a neurologist tells me I need another exam … Go ask Trump for his, OK?”

“I am not opposed, if my doctors tell me,” he added. “If my doctors think I need another exam, I’ll do it.”

His mistake with Harris’s name came just hours after he accidentally called Ukraine President Volodymyr Zelensky “President Putin.” He quickly caught his error, turning back to a lectern to say “we’re going to beat President Putin.”

“I’m so focused on beating Putin,” he said.

Zelensky appeared to shrug off the slip, joking “I’m better.”

“You’re a hell of a lot better,” Biden told him.

The press conference follows more than two weeks of pressure from a growing number of Democratic officials, donors and voters calling on the president to hang up his re-election campaign.

Biden has framed the 2024 election as the most important in his lifetime and depicted his Republican rival as an imminent danger to American democracy, yet Biden insists he remains the best candidate to defeat him, as he did four years ago.

In campaign rallies in the aftermath of the June 27 debate, Biden has suggested that “elites” are plotting against him, and that the push to end his campaign is coming from powerful unseen opponents.

Yet it appears to be precisely the opposite — Democratic officials are now fuming that White House officials and campaign aides are ignoring voter concerns about Biden’s age and fitness that have been an issue since before the debate, or, worse, that his staff has been actively covering up signs of the president’s decline.

More than a dozen Democratic members of Congress have publicly called on the president to end his campaign, and reports of dissent among congressional Democrats and officials across the US is building up pressure on Biden’s campaign to address concerns head on and at least prove that he is a more than viable candidate to defeat Trump.

Most Democratic voters nationwide believe Biden should step aside, according to Thursday’s ABC News/Washington Post/Ipsos poll. Sixty-seven percent of US adults believe Biden should end his campaign, including 56 percent of Democrats.

But the poll shows that Biden and Trump largely remain in a dead heat, while other post-debate polls have shown Biden trailing Trump by 3.5 percentage points on average. Biden’s campaign has argued that his debate performance has not significantly moved the needle.