Joe Biden rejects polling numbers and says he'll only drop out if the Lord Almighty tells him to — where does his broadcast interview leave his campaign?

The future of a career in politics that has spanned more than 50 years came down, it seemed, to 22 minutes.

That's how long the US president sat down with ABC News America anchor George Stephanopoulos in an exclusive television interview in the wake of his disastrous debate performance.

The interview, ABC said, was broadcast in full with no edits.

As a growing number of Democrats now publicly mull whether and how they could replace the 81-year-old before November's election, Joe Biden really had to pull something out of the hat.

The president didn't lose his train of thought, most of his sentences were coherent and his voice was a lot stronger than on debate night, when he says he was suffering from a "really bad cold".

But Joe Biden, it seemed, was living in some kind of a parallel world to the Democrats who are so worried about his physical and mental fitness they think Donald Trump will secure a second term if they don't swap him out.

The octogenarian flat out denied he was more frail than when he took office three-and-a-half years ago.

Yet he repeatedly deflected questioning on whether he'd take a neurological test to prove that, claiming his daily workload amounted to a cognitive test.

He said he didn't accept his dismally low approval rating of 36 per cent.

"That's not what our polls show."

He also didn't accept his poll numbers against Donald Trump had dropped since the debate.

"The pollsters I talk to tell me it's a toss-up."

He didn't accept that his colleagues were turning on him.

Sure, he'd seen "in the press" that there were calls from some within the party for him to stand aside, but "the vast majority are not where those folks are".

In possibly the strongest sign that Joe Biden is really, really digging his heels in, he said he would only stand aside if God told him to.

"If the Lord Almighty comes down and tells me that, I might do that," he said.

Note the use of the word "might".

The Texas congressman who became the first sitting Democrat in the House to call on Joe Biden to end his candidacy, was troubled by what he saw.

"The need for him to step aside is more urgent tonight than when I first called for it on Tuesday," Lloyd Doggett told CNN.

"We may not be the Lord Almighty," but "Mr president, the risk of a Trump presidency, to destroy our democracy, to take over the government and never give it back again, is so great that we have to have our strongest candidate."

American presidents are not known for their humility, but on Friday Joe Biden's hubris was jarring.

"I don't think anybody's more qualified to be president or win this race than me", he declared.

"Not only am I campaigning, but I'm running the world," he said.

"Not-- and that's not hi-- sounds like hyperbole, but we are the essential nation of the world."

The above quote is taken from ABC's America's official transcript of the interview and highlights the somewhat faltering way in which Joe Biden speaks, even on a good day.

These verbal stumbles are now no longer being attributed solely to his stutter, but being pored over for any sign of mental decline.

This definitely was not a bad day for Joe Biden.

As an exercise in damage control eight days after the fateful debate, the interview went about as well as the president could have hoped for.

Had it been disastrous, the calls would have become even louder and clearer that he make way for Vice-President Kamala Harris or another candidate.

Joe Biden also appeared energised and feisty at a campaign event earlier in the battleground state of Wisconsin, telling the crowd he was "staying in the race", even though "they're trying to push me out".

Who knows if he saw some of the signs held by protesters as he made his way into the venue.

"Pass the torch," one said.

"Give it up, Joe."

"Pres Biden — serve your country — not your ego… exit now."

The president has probably done enough to buy himself a little more time.

"I can't wait to help him continue to take the fight to Trump and win in November," key ally Senator Chris Coons enthused soon after the interview was broadcast.

But while he admitted to having a bad debate night, Joe Biden appeared in denial about just how awful it was.

Perhaps that's because he says he hasn't watched it back, another worrying sign for those who think the president is to an extent being shielded from his own decline.

More tests will come thick and fast.

There's a NATO meeting in Washington next week.

It's a chance for the president to shine, but comes with inherent risk.

It's hard to escape the sense that Joe Biden is only treading water, and that it won't be long before he has another moment.

The president again used a teleprompter at the campaign event.

He did make a brief unscripted stop in an overflow room after coming off the stage, taking time to chat to an 11-year-old.

"Leo, my name's Joe," the president said.

"When I was 11, I came up to about your shoulder."

The comment got a laugh from the small crowd of supporters, and the moment re-enforced the president's ability to connect with ordinary voters.

But he'll need to convince a tougher audience than Leo if he's to see out the next four months.