Mr Biden faces an even taller task this week domestically.

The president has pointed to buttressing and expanding Nato in the face of Russian aggression as one of his key accomplishments.

This is something that differentiates his leadership from Trump’s - as well as any Democrats who could potentially replace him on the ballot - and the summit will be his chance to put that on display for the American public.

“Who’s going to be able to keep Nato together like me?” the president said in his interview with ABC’s George Stephanopoulos on Friday. He added that the Nato summit would be a good way to judge his abilities.

“Come listen,” he said. “See what they say.”

But simply clearing low expectations at the Nato summit and the Thursday press conference may not be enough for many of the politicians, pundits and party activists who are already calling for him to step aside.

“Just having some good appearances is not going to stop the questions,” said Bill Scher, a liberal pundit and editor of Washington Monthly who recently penned a column calling for Mr Biden to step aside for Vice-President Kamala Harris.

“Time was really of the essence to nip all the speculation in the bud, and they wasted a week. There is no clear path out of this situation.”

Mr Scher - a longtime supporter of Mr Biden - says the president’s attempts to push back now with media interviews, letters and calls to Democratic politicians come after public sentiment has solidified against him.

And once that sentiment is fully cemented in the polls - which could take several weeks - it will probably be too late to cleanly replace him.

“I understand how difficult it has to be when you’re nearing the end of your life and you’re not performing as well as you used to,” Mr Scher said. “Having to come to terms with that in public has to be excruciating.”

But the data that shows Mr Biden losing support and facing defeat in November is becoming increasingly clear.

Polls indicate nearly three-quarters of Americans - and even a majority of Democrats - think the president should stand down. A half-dozen Democratic members of Congress have called for him to abandon his bid, and many others have offered only equivocal support.'

The president continues to say he will press ahead with his campaign, however, and he has the national convention delegates to ensure that he is the Democratic nominee. The decision lies firmly in his hands, and if he can make it through the week without a major misstep, he may, in fact, survive the immediate storm.

The story of this week, however, has been set. It isn’t one of Nato celebrating its 75th year of existence and focusing on the challenges to come.

Instead, it is a narrative that could decide whether Mr Biden can politically live to fight another day.'