In one of the most consequential press conferences of his political career, President Biden defended his foreign and domestic leadership, stumbling several times in his bid to prove he’s fit for another four years in office despite his 81 years.

Mr. Biden defended his gaffes, including a major mix-up at the NATO summit hours before he met with the press, while at the same time making new mistakes and at times sounding inaudible or incoherent.

Mr. Biden defended his presidency vigorously in the nearly hour-long conference, pledging he is the most qualified person to serve as president and one who is capable of winning in November over former President Donald Trump, the presumed Republican nominee.

“I beat him once and I’ll beat him again,” Mr. Biden said.

At the same time, the president coughed and stumbled at times and frequently spoke in a near whisper.

There were more word mix-ups, which have now become characteristic of Mr. Biden’s public addresses.

When it came time to answer a question about Vice President Kamala Harris possibly succeeding him on the ticket, he identified her as “Vice President Trump.”

He said, “I wouldn’t have picked her if she wasn’t qualified to be president.”

Mr. Biden denied needing to go to bed early despite reports that he told Democratic governors he needed to retire at 8 p.m.

But he also explained,“it would be smarter to pace myself a little more,” and not be on the job from early in the morning until very late at night.  

“My schedule has been full bore,” Mr. Biden added, taking a swipe at his opponent.

“Where has Trump been? Riding around in his golf cart, filling out his scorecard before he hits the ball? I always have an inclination, just to keep going, not stopping. I’ve just got to pace myself a little more,” Mr. Biden said.

He also stumbled over questions about U.S. aid to Ukraine and the country striking directly at Russia, telling reporters, “our military is working on following the advice of my commander in chief, my my chief of staff of the military, as well as the Secretary of Defense and our intelligence people,” when it comes to U.S. involvement.

He attempted to navigate a question about how he will handle the growing alliance between Russia and China but part of it was rambling.

He answered a follow-up question about whether he’d be capable of negotiating face-to-face with Russian President Vladimir Putin or Chinese President Xi Jinping in two or three years.

“I’m ready to deal with them now and three years from now. Like I said, I’m dealing with Xi right now, in direct contact with him. I have no good reason to talk to Putin right now. There isn’t any world leader I’m not prepared to deal with. I’m not ready to talk to Putin unless Putin is ready to change his behavior,” he said.

The president took questions from the press in a bid to prove his cognitive mettle following a disastrous debate performance two weeks ago and amid increasing calls from within his own party for him to quit the race and hand the baton, presumably to Ms. Harris.

The president arrived at the press conference following a bad stumble at NATO, right in front of world leaders gathered in Washington, where he’s worked this week to prove he’s a capable leader.

After a day of talks with Ukrainian President Volodymyr Zelenskyy, Mr. Biden introduced him as “President Putin,” the Russian president who invaded his country.

Mr. Biden immediately corrected and attempted to explain himself but the gaffe exploded on social media and led the evening news, adding to Mr. Biden’s struggle to prove he’s cognitively fit for office.

He’s facing rising pressure from Democrats to move aside for Ms. Harris or another Democratic candidate ahead of the Democratic National Convention in Chicago, which begins on Aug. 19.

Senate Democrats met with Biden staffers Thursday on Capitol Hill and left no more confident Mr. Biden could pull off a win against former Mr. Trump.

A Washington Post Ipsos poll released Thursday showed Mr. Biden and Mr. Trump tied nationally, which has largely been the case for months. But the same poll showed two out of three Americans believe Mr. Biden should not run for reelection, including three-quarters of critical independents and more than half of all Democrats.

• Susan Ferrechio can be reached at sferrechio@washingtontimes.com.