(Bloomberg) -- President Joe Biden said he may have decided to serve just one term if Donald Trump were not seeking to return to the White House, arguing the former president poses a grave threat to American democracy. 

Biden, 81, has faced persistent voter doubts about his decision to seek four more years in office due to his age. The president has sought to parry those concerns in part by saying he is motivated to defeat Trump again and prevent him from holding power. 

“If Trump wasn’t running, I’m not sure I’d be running,” Biden, 81, told donors Tuesday at a campaign fundraiser in Massachusetts. “But we cannot let him win for the sake of our country.” 

The president has recently stepped up his warnings that Trump would dismantle the US’s democratic institutions, roll back laws that allow more people to access health care and push more restrictions on abortion rights.

Nonetheless, his comment raised eyebrows because it played into worries about his age and lack of voter appetite for a Biden-Trump rematch. Polls have shown most Democrats, do not want Biden to be their party’s nominee due to concerns about his ability to handle the job.

Biden sought to downplay his remark later Tuesday. 

“I expect so,” Biden said when asked by a reporter at the White House if he would be running if Trump was not. “But look, he is running and I have to run.”

The president also said he would not drop out if Trump does. 

Earlier: Biden’s Campaign Expects to Raise $15 Million in Five Days

Biden has repeatedly said Trump’s reaction to the 2017 white supremacist rally in Charlottesville, Virginia, encouraged him to seek the presidency in 2020, citing his predecessor’s remarks after a counter-protester was killed that there were “very fine people” on both sides of the demonstrations.

The president’s advisers have said he is the best candidate to defeat Trump a second time, backing up his decision to seek reelection. 

Biden, who celebrated a birthday last month, is already the oldest president in US history. Allies and people who interact with him say the focus on his age and health is unfair and that he is fit enough to serve. They point to his work schedule and exercise routines prescribed by the White House physician.

Earlier: Biden’s 81st Birthday Highlights Biggest Liability for 2024

The president has insisted he is able to serve another term, even as he tries to defuse concerns about his age with humor. At another fundraiser earlier Tuesday, Biden joked about being an octogenarian. 

“It’s hell turning 40 twice,” he said.

With Trump, 77, leading the GOP field by a wide margin, Biden has increasingly targeted his predecessor, treating him as the de facto nominee. That focus also comes as polls show Biden trailing Trump in a potential head-to-head match-up, fueled in part by worries over the president’s age and voter perceptions of his handling of the economy.

Read more: Wall Street Icons Lament Biden, Trump as Top 2024 Choices

Prominent Wall Street leaders have also expressed dismay at the prospect of a Biden-Trump rematch in November and are eyeing other candidates for a potential eleventh-hour push to shake up the race.

Billionaire investor Bill Ackman said last week that Biden risks damaging his reputation if he seeks a second term, urging him to “step aside” and “create the opportunity for some competition.” Ackman said he was watching Minnesota Representative Dean Phillips, 54, who is pursuing a long-shot challenge against Biden for the Democratic nomination.

“Biden’s done a lot of good things. But I think his legacy will not be a good one if he is the nominee,” Ackman said in an interview with Bloomberg Television.  

JPMorgan Chase & Co. Chief Executive Officer Jamie Dimon said voters should support former South Carolina Governor Nikki Haley, 51, as an alternative to Trump for the Republican nomination. 

“Even if you’re a very liberal Democrat, I urge you, help Nikki Haley too,” Dimon said at the New York Times Dealbook Summit last week.

--With assistance from Jennifer Jacobs and Ashleigh Carrington Fields.

(Adds more Biden comments starting in 6th paragraph)

©2023 Bloomberg L.P.