Joe Biden's birthday on Monday underscored an issue of mounting concern for Democrats.

At 81 years old, Biden is facing growing skepticism from all corners of his fitness for office, and Democrats are worried he could lose re-election to Donald Trump.

Biden turns 81

Biden has often tried to defuse the concern with self-deprecating humor, and he made another valiant attempt during the traditional Thanksgiving turkey pardoning Monday.

"I just want you to know it's difficult turning 60. Difficult," Biden said. "This is the 76th anniversary of this event. I want you to know I wasn’t there for the first one," he added.

There's no sign that Biden's jokes are putting the country at ease. Polls universally show that voters believe Biden is too old for his job, a concern that is not widely shared about President Trump.

Biden also gets poor reviews on his job performance, especially where the economy is concerned. Biden has struggled to sell "Bidenomics" as inflation continues to bring pain for American families.

A number of polls have shown voters trust Trump more than Biden on the economy, and the chaotic state of the world - with war raging in Europe and the Middle East - has done little to quiet concerns that Biden is too old to handle the responsibilities of his very important office.

A photo of Biden's 81-candle birthday cake went viral, with many calling the dessert - which resembled a fireball - an ironic statement on his shambolic presidency.

President Biden is celebrating his 81st birthday.

That cake is America right now. pic.twitter.com/jXHmdWrD7f

— Kyle Becker (@kylenabecker) November 21, 2023

Trump gains traction

A spate of recent polls from pro-Biden outlets like the New York Times and NBC News show Biden losing to Trump a year from now.

In a surprising twist, polls show Trump gaining traction with young voters, a traditionally left-leaning bloc that was critical to Biden's coalition in 2020.

A new NBC poll found Trump topping Biden with young voters by four points - and Trump beating Biden overall for the first time in the poll's history.

While concerns are rising in Democratic circles, Biden can rely on a team of loyal staffers who are willing to say just about anything to defend him.

"Our perspective is that it's not about age. It's about the president's experience," press secretary Karine Jean-Pierre said.

"I would put the president's stamina, the president's wisdom, ability to get things done on behalf of the American people up against anyone of any day of the week."