"I promise you," said U.S. President Joe Biden, as he stood before a small crowd of supporters crammed into a Detroit diner – including a 4-year-old boy with a halo of blond hair, named Beau like the president's beloved late son – "I am OK."
Young Beau gazed up at the 81-year-old president from his mother's lap and giggled as Biden spoke in an automotive-themed diner in Detroit's wealthy western suburbs.
Biden joked about his age – "I'm only 41" – he said, to laughs – but the tone of Friday's campaign swing through the battleground state of Michigan was serious just weeks after a disastrous debate performance raised concerns over his fitness for reelection.
"I am running, and we are going to win!" he said to cheers, hours later, at a packed high school gym in central Detroit.
Biden also used the rally before 2,000 ramped-up supporters to lay out a series of campaign promises, including enshrining abortion in law, increasing voter access, expanding entitlement programs, banning assault weapons, curbing housing costs and more – all, he said, by "making the wealthy pay their fair share," which he defined as a 25% minimum tax on billionaires.
He also threw unprecedented amounts of shade – both serious and spurious – at his 78-year-old Republican opponent, joking: "Trump doesn't get out of his golf cart."
But also: "It's time for us to stop treating politics like entertainment and reality TV," he said. "Another four years of Donald Trump is deadly serious."
Those firm words come up against growing concerns about his prospects – not from his detractors, but from within the Democratic Party. On Friday, en route to Michigan, campaign officials pushed back and brushed aside the worries.
"He is laser-focused on demonstrating that he is the best possible person to take on Donald Trump in November," said Biden campaign spokesperson Michael Tyler, speaking to reporters on Air Force 1.
And in Washington, Biden's allies are on the attack in his defense.
"Joe Biden is focused on the future of this country," South Carolina Representative James Clyburn told NBC News' Today Show. Clyburn is a staunch supporter credited with helping deliver the Black vote to Biden in 2020. "And I always say the best predictor of future performance is past behavior."
But not all Democrats agree. On Thursday night, Biden took nearly an hour of questions from reporters, on everything from his health to the future of NATO and his strategy for countering an emboldened China. But a new campaign, called "Pass the Torch," on Friday released a scorching review of his performance, during which he accidentally referred to his vice president as "Vice President Trump." Her name is Kamala Harris.
"Great job, Joe!" Trump posted on his social media platform.
"We cannot be holding our breath during every campaign speech and appearance," said Aaron Regunberg of Pass the Torch. "We need a candidate who is able to campaign vigorously against Donald Trump."
On Thursday, Biden also drew gasps by calling Ukrainian President Volodymyr Zelenskyy by his nemesis' name, introducing him at the NATO summit as "President Putin," for Russian President Vladimir Putin. He quickly corrected the mistake, but it was pounced upon by his political opponents – and his allies.
"This is a gaffe – by itself it's not a massive deal," Regunberg said in a statement. "But it's concerning that the president can't seem to get through a single event without making a mistake that could provide grist to the Trump attack machine."
Washington state Democratic Senator Patty Murray agreed, saying: "We need to see a much more forceful and energetic candidate on the campaign trail in the very near future in order for him to convince voters he is up to the job."
And academics say Biden's main enemy here is simple math.
"I'm not sure how he's going to overcome the 'too old' aspect because all of us have calendars and can count," said Shannon O'Brien, an associate professor of instruction at the University of Texas at Austin. "However, just because you're old doesn't mean you're not vital. And just because you're old doesn't mean you're impaired. And I think he needs to show that he's vigorous and that he is mentally adept and that he understands the issues."
On Friday, a confident Biden, energized by the packed crowd of supporters – some of whom began singing the national anthem while waiting for him to appear, led by a soaring alto somewhere deep in the crowd – zeroed in on what he sees as the real weak link in this election.
"I know I look 40 years old," Biden said. "I know I'm a little bit old. Hopefully with age comes a little bit of wisdom. And here's what I know: I know how to tell the truth. I know right from wrong. … And I know Americans want a president, not a dictator."
