Ever present by the US president's side after his calamitous debate -- and foursquare behind him as he vowed to fight on in his reelection bid -- First Lady Jill Biden has been fighting her husband's battles from the front lines.
"I think she is as influential as pundits are claiming and her opinion likely matters more to him than anyone else's," said Tammy Vigil, a professor of communications at Boston University.
"Without her support, it would be impossible for him to continue in the race."
The 73-year-old community college professor was making headlines of her own on Monday, as Vogue unveiled the cover of its August issue -- with the first lady looking seraphic in a long white tuxedo gown by Ralph Lauren.
The picture and the article date from April, long before President Joe Biden struggled to make himself understood during a halting, unfocused performance at a CNN debate against Republican rival Donald Trump.
But in a note introducing the article, the magazine's editors revealed they'd had a telephone conversation with the first lady shortly after the debate, as calls mounted for her 81-year-old husband to withdraw his candidacy.
She told Vogue the Biden family "will not let those 90 minutes define the four years he's been president."
The woman who has shared her last 47 years with the Democratic leader also told a weekend meeting of donors: "Joe isn't just the right person for the job. He's the only person for the job."
On Thursday, after the debate, Jill Biden was shown taking her husband's arm to help him down a few steps in the CNN studio.
The following day, she was there again in a dress that read "vote," as a much more energetic Joe Biden headlined a rally in North Carolina.
Before they married in 1977, Joe Biden had been turned into a widower by a horrific car crash five years earlier that had claimed the lives of his first wife and their infant daughter. His two boys, Beau and Hunter, survived.
The family was revisited by tragedy years later as Beau, a cherished son at the start of what looked like a promising political career of his own, died of cancer.
Adding to the family's difficulties, Hunter struggled for years with a crack addiction.
The first lady is now the center of gravity of the troubled but burgeoning clan, bolstered with the birth of Jill and Joe's daughter Ashley a few years after their wedding -- and eventually the arrival of their grandchildren.
Without her support, the Democrat would not have embarked on his quest for a second term.
When she arrived at the White House, she continued to teach English at a college near Washington, unheard of for a president's wife.
Meanwhile, she assumed the traditional role of first lady -- in charge of Christmas decorations and gala dinner menus, as well as promoting pet causes -- in her case, literacy.
Amid the shaky reelection campaign, Jill Biden could well encourage an outpouring of sympathy with her passionate advocacy for the president since his calamitous showdown with Trump -- but also risks alienating a segment of public opinion by doing so.
"A contemporary US first lady is supposed to be the 'not-so-secret weapon' that helps her husband by attesting to his character and by helping raise funds, et cetera. Because of that, Jill Biden is expected to participate in the campaign," said Vigil.
"However, there are also unstated limits to that activity that are hard to figure out until a particular line is crossed. If she is too vigorous in her support and defense of her husband, people will complain."
The first lady has become a prime target on social media since the debate, with Trump supporters painting her as an unscrupulous manipulator.
"What Jill Biden and the Biden campaign did to Joe Biden tonight -- rolling him out on stage to engage in a battle of wits while unarmed -- is elder abuse, plain and simple," Wyoming Republican Harriet Hageman posted on X after the debate.
