Jill Biden could convince Joe to drop out. So far, she's vowing to fight on.

Joe Biden's debate disaster has top Democrats questioning his viability, but First Lady Jill Biden stands firm in support of her husband.

• Democrats think Jill Biden might be the only person who could convince Joe Biden to drop out.
• After Biden's debate performance, some Democrats have been questioning his ability to defeat Trump. 
• But the first lady isn't backing down. And so, neither is the president.

Joe Biden's debate performance last week was, by most accounts, a disaster.

But First Lady Jill Biden — possibly the only person who could convince the president to call it quits — is standing beside him.

Since the president bungled the debate against Trump on Thursday, some top Democrats and Biden loyalists have been questioning Biden's viability as a candidate, with some even calling on him to drop out of the race.

Biden's close personal friend and a columnist for The New York Times, Thomas Friedman, wrote in a Times article the morning after the debate, "Joe Biden, a good man and a good president, has no business running for re-election."

R.T. Rybak, a former DNC vice chair and former Minneapolis mayor, urged his fellow Democrats to push Biden to step down, in a post on Facebook.

But Politico reported, citing Democrats close to Biden, that the only person who could convince him to step down is the first lady.

Hank Sheinkopf, a veteran Democratic political consultant, echoed that sentiment, telling The Guardian, "The most logical person to suggest to Biden he not do this for his health and for the good of the country is Jill Biden."

But so far, the first lady is vowing to fight on.

Speaking at a fundraiser in Manhattan on Friday, Jill Biden acknowledged her husband's lackluster debate performance, telling a group of supporters, "As Joe said earlier today, he's not a young man," according to The Washington Post.

"After last night's debate, he said, 'You know, Jill, I don't know what happened. I didn't feel that great,'" Jill Biden continued, according to the Post.

But, she added, "What my husband does know how to do is tell the truth," the outlet reported. "When he gets knocked down, Joe gets back up, and that's what we're doing today."

Jill Biden reiterated this stance to Vogue on Sunday, telling the outlet that the Biden family "will not let those 90 minutes define the four years he's been president."

"We will continue to fight," she added, according to Vogue.

And she's not the only Biden standing firm. During a gathering at Camp David this weekend, other members of Biden's family, including his son Hunter Biden, urged the president to stay his course, according to a report from The New York Times.

Jill Biden and the rest of the family have argued that the president should be defined by his successes in the White House, not by one debate performance.

But even some Biden supporters are arguing that his lackluster debate performance has already sealed his fate as an aging candidate incapable of beating Trump this November.

Unless Jill Biden changes her tune or Joe Biden is offered a dignified way out, it doesn't seem likely that the president will back down. But with the Democratic National Convention — where Biden is expected to get the party's formal nomination — not happening until August, there's still time for a major campaign shake-up.