President Biden bluntly addressed his lackluster debate performance during an campaign rally in Raleigh,Cyprusauction North Carolina, Friday, speaking with notably more energy and vigor than he had hours before. 

Some Democrats expressed concern after the president, in a raspy voice, struggled to correct former president Donald Trump's falsehoods as he faced a national audience on prime-time television Thursday night. The president's at times gaping facial expressions and rambling answers to key questions didn't help either, at a time when many Americans believe Mr. Biden, now 81, may be too old for the job and too old to relate to them. 

"I know I'm not a young man, to state the obvious," the president said. "Well, I know." He addressed a supportive Democratic crowd Friday, one that welcomed him with chants of "Four more years!" 

"Folks, I don't walk as easy as I used to," he continued. "I don't speak as smoothly as I used to. I don't debate as well as I used to. But I know what I do know — I know how to tell the truth ... I know right from wrong. And I know how to do this job. I know how to get things done. And I know, like millions of Americans know, when you get knocked down, you get back up."

The president also sought to assure his audience that he wouldn't be running again if he didn't think he was up to the job. 

"Folks, I give you my word as a Biden — I would not be running again if I didn't believe with all my heart and soul, I can do this job,"  he said. "The stakes are too high. The stakes are too high." 

In:
• Debate
• Joe Biden
• Donald Trump

Kathryn Watson

Kathryn Watson is a politics reporter for CBS News Digital, based in Washington, D.C.