Washington — In the first moments of Thursday's debate, President Biden stumbled as he flubbed some early lines as his voice appeared ready to give out, while sources said he was suffering from a cold.  

Mr. Biden's voice never recovered throughout the 90-minute debate against former President Donald Trump — deflating chances of convincing Americans through his debate performance that at age 81, he's healthy enough to serve another four-year term in the White House. A CBS News poll earlier this month found that only a third of voters think Mr. Biden has the cognitive ability to be president, compared to half of voters who think Trump does.

Forty-five minutes into the debate, sources familiar with Mr. Biden's debate preparations said he has had a cold for the past few days. A top official said the president was examined by a doctor at Camp David, who confirmed the cold. The president tested negative for COVID, they said. 

In addition, the president lost his train of thought and struggled to name Medicare when he was answering a question about the tax rate for wealthy Americans.  

"We have 1,000 trillionaires in America — I mean billionaires in America. And what's happening? They're in a situation where they, in fact, pay 8.2% taxes, if they just paid 24%, 25% — either one of those numbers — we'd raise $500 million dollars — billion dollars, I should say — in a 10-year period," he said, listing off a number of priorities like paying for child care, health care and "making sure that we're able to make every single solitary person eligible for what I've been able to do with the COVID, excuse me, with, dealing with everything we have to do with, uh…" 

The president then paused and struggled to come up with the word. 

"Excuse me," he said, "dealing with everything we have to do with…" 

The president then paused again. 

"Look, if we finally beat Medicare," he continued. 

"Thank you, President Biden," CNN moderator Jake Tapper said. "President Trump?" 

"He did beat Medicaid, beat it to death, that he's destroying Medicare," Trump said. 

Mr. Biden's debate performance rattled some Democrats, with one House Democrat familiar with the conversations saying, "I've never seen a freakout like this." But the House Democrat cautioned it's unclear how seriously they'd push for Mr. Biden to step down from the 2024 ticket. 

One high-level Democratic Capitol Hill source described the resident's performance as "disappointing" and "painful" but believes it's still possible for him to "rebound."

The morning after the debate, House Democratic Leader Hakeem Jeffries, asked whether Mr. Biden should step aside after a debate performance, replied, "No."

Mr. Biden and Trump were asked later in the debate to address concerns about their capability to be president at their age.

"I spent half of my career being criticized being the youngest person in politics. I was the second youngest person ever elected to the United States Senate and this guy's three years younger and a lot less competent," Mr. Biden said, telling voters to look at his record. "Look at what I've done."

Trump, meanwhile, claimed he has passed two cognitive tests.  

Mr. Biden's sounded more energetic post-debate when he addressed supporters at a watch party, with his voice appearing to return with excitement.

Nancy Cordes, Nikole Killion, Ed O'Keefe and Ellis Kim contributed reporting. 

In:
• Debate
• Joe Biden
• Donald Trump
• 2024 Elections

Caitlin Yilek

Caitlin Yilek is a politics reporter at CBSNews.com, based in Washington, D.C. She previously worked for the Washington Examiner and The Hill, and was a member of the 2022 Paul Miller Washington Reporting Fellowship with the National Press Foundation.

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