After Biden's debate performance, top Democratic fundraisers raise concerns.

• Some top Democratic donors are privately expressing concern over President Biden's poor debate performance against Trump.
• Already, some of the Democratic Party's top fundraisers had contacted CNBC after just 15 minutes of the debate, expressing their worries about Biden's performance.

Several high-ranking donors to the Democratic Party are privately expressing concern following President Biden's poor showing in Thursday's debate against former President Trump.

A Biden donor who plans to attend a fundraiser with the president on Saturday in the Hamptons stated that it was a "disaster."

The person, who was granted anonymity to recount private conversations, stated that the situation was terrible and worse than they had anticipated. Everyone they were speaking with believed that Biden should drop out.

CNN's 90-minute debate hosted by CNN began receiving concerns from Democratic campaign donors and fundraisers within 20 minutes.

A longtime Democratic campaign advisor who has been raising money for congressional leaders for over a decade and helped raise money for Biden's 2020 White House bid declared "Game over."

The advisor stated that Biden must depart immediately or risk being crushed, as they planned to discuss the debate with Democratic National Committee Chairman Jaime Harrison on Friday.

The advisor of a prominent Democratic Party donor described the debate as a "complete disaster" for Biden, surpassing even the poor performances of Ronald Reagan in 1984, George W. Bush in 2004, and Barack Obama in 2012.

Biden's difficulties at the debate began immediately. He seemed to lose his train of thought and paused for extended periods, prompting CNN moderators to interrupt him while he was discussing U.S. health care.

Biden said, "Ensuring that every person is eligible for what I've been able to do with the Covid pandemic, excuse me, with dealing with everything we have to do with, look..."

President Biden thanked Jack Tapper after stating that they had finally defeated Medicare.

During the debate, the president repeated himself or remained silent for several seconds at times. Biden's voice was hoarse and low throughout the evening.

Mitch Landrieu, Biden's campaign co-chair, stated that the president's cold was the reason for his poor performance in the debate. According to Landrieu, people will initially focus on the physical aspect of the debate.

"Despite not being at his best, Biden still delivered a strong finish," Vice President Kamala Harris acknowledged in a CNN interview on Thursday.

Biden's sentence on border security was difficult to follow.

Biden stated, "I will keep moving until we achieve a complete ban on the initiative, in relation to increasing Border Patrol and asylum officers."

"I don't know what he said at the end of that sentence. I don't think he knows what he said, either," the former president quipped.

Representatives for the Biden campaign did not respond to requests for comment.

It would be challenging to replace Biden on the ticket with less than two months until the Democratic National Convention in August, as the president would have to drop out of the race and leave the decision about a nominee to the delegates at the convention.

According to Kate Bedingfield, former White House communications director in the Biden administration until 2023, Joe Biden's debate performance was truly disappointing and there's no other way to view it.

She stated that his main challenge was demonstrating to the American public that he possessed the necessary energy and endurance, which he failed to accomplish.