Anonymous sources reportedly close to President Biden have allegedly witnessed "15, 20 occasions in the last year and a half" similar to what the country saw at last week's presidential debate. 

"These are people, several of them who are very close to President Biden who loved him, have supported him and among them are some people who would raise a lot of money for him. And they are adamant that what we saw the other night, the Joe Biden we saw, is not an a one-off, that there have been 15, 20 occasions in the last year and a half when the president has appeared somewhat as he did in that horror show that we witnessed," CNN's Carl Bernstein told Anderson Cooper Monday night, referring to the debate. 

"And what's so significant is the people that this is coming from, and also how many people around the president are aware of such incidents, including some reporters incidentally who have witnessed some of them," he said.

Alluding to Biden's address to the nation in reaction to the Supreme Court immunity ruling involving the Trump legal cases Monday, Bernstein continued, "But here we see tonight, that, as these people say, President Biden at his absolute best, and yet these people who have supported him, loved them, campaigned for him, see him often, say that in the last six months particularly there has been a marked incidence of cognitive decline and physical infirmity."

BILL MAHER GETS BLUNT WITH FELLOW DEMOCRATS ON BIDEN: ‘HE IS GOING TO LOSE, IT’S SO APPARENT'

The 80-year-old veteran journalist alleged that the sources he spoke with said that over the past year they warned top Biden ally Ron Klain, who oversaw debate prep at Camp David, that they "have a problem," telling the Biden confidant of instances where the president has "lost his train of thought" and "can't pick it up again."

"There was a fundraiser at which he started at the podium. And then he became very stiff, according to the people there, as if it were almost a kind of rigor mortis," Bernstein said. "This was a year ago almost exactly at the old Four Seasons restaurant on Park Avenue. And he became very stiff and a chair had to be brought for him to do the latter part of the event." 

"I think that what these folks are saying and have been saying for a while is, 'Yes, he's great when we see him, as we have tonight. But he also has these inexplicable moments that we're very concerned about and you, Ron Klain, and the First Family, we need to talk about this.' And they've been pushed back repeatedly whenever it's been brought up," he continued.

BIDEN'S ‘DISASTER’ DEBATE PERFORMANCE SPARKS MEDIA MELTDOWN, CALLS FOR HIM TO WITHDRAW FROM 2024 RACE

While Bernstein said his sources insist Biden has been "sharp" in his national security meetings, he suggested the country is "dealing with two sets of one person." 

"And it really needs to be explored, according to the people I'm talking to," Bernstein said. "And I think an awful lot of major Democrats believe this, including some who have made statements to the contrary. But this is a problem that's not gonna go away."

Neither the White House nor the Biden campaign immediately responded to Fox News Digital's requests for comment.

MEDIA FIGURES SHOCKED AT BIDEN'S 'BAD' DEBATE PERFORMANCE: ‘TOTAL AND COMPLETE DISASTER’ 

Biden's shocking debate performance has become a political earthquake with wide swaths of the liberal media calling for him to withdraw from the presidential race. 

"Mr. Biden has been an admirable president. Under his leadership, the nation has prospered and begun to address a range of long-term challenges, and the wounds ripped open by Mr. Trump have begun to heal. But the greatest public service Mr. Biden can now perform is to announce that he will not continue to run for re-election," The New York Times editorial board wrote Friday.

However, top Democrats are rallying behind Biden, including former President Obama.

"Bad debate nights happen. Trust me, I know," Obama said in a statement Friday. "But this election is still a choice between someone who has fought for ordinary folks his entire life and someone who only cares about himself. Between someone who tells the truth; who knows right from wrong and will give it to the American people straight — and someone who lies through his teeth for his own benefit. Last night didn’t change that, and it’s why so much is at stake in November."

President Biden slammed the Supreme Court's ruling on presidential immunity in Trump v. United States, saying it means there are virtually no limits on what a president can do, in a speedy address Monday evening.

The president spoke for less than five minutes – four minutes and 40 seconds to be exact – before turning his back to the press and walking away. 

"This is a fundamentally new principle, and it's a dangerous precedent, because the power of the office will no longer be constrained by the law, even including the Supreme Court of the United States," Biden said.

The Supreme Court ruled that a former president has substantial immunity from prosecution for official acts committed while in office, but not for unofficial acts.

TRUMP IMMUNITY CASE: SUPREME COURT RULES EX-PRESIDENTS HAVE SUBSTANTIAL PROTECTION FROM PROSECUTION

In a 6-3 decision, the Court sent the matter back down to a lower court, as the justices did not apply the ruling to whether or not former President Trump is immune from prosecution regarding actions related to efforts to overturn the results of the 2020 election.

Biden continued his address, saying that the American people must decide whether Donald Trump's assault on democracy on January 6th makes him "unfit" for public office and the highest office in the land.

"The American people must decide if Trump's embrace of violence to preserve his power is acceptable. Perhaps most importantly, the American people must decide if they want to entrust the presidency to Donald Trump once again. Now knowing, he'll be even more emboldened to do whatever he pleases, whenever he wants to do it," Biden said.

Biden also spoke about the character of the nation's first president, George Washington, and how he believed power was limited, not absolute.

Biden wrapped his speech and dodged questions from reporters as he left abruptly. 

Reporters shouted questions at Biden, asking him if he plans to drop out of the presidential race following his debate with Trump. 

TRUMP TOUTS SUPREME COURT'S PRESIDENTIAL IMMUNITY RULING AS 'BIG WIN FOR OUR CONSTITUTION AND FOR DEMOCRACY'

Biden has not taken questions from the press and has used teleprompters at his events, including a fundraiser in the Hamptons, following his disastrous debate performance against Trump last week.

"Today’s Historic Decision by the Supreme Court should end all of Crooked Joe Biden’s Witch Hunts against me, including the New York Hoaxes - The Manhattan SCAM cooked up by Soros backed D.A., Alvin Bragg, Racist New York Attorney General Tish James’ shameless ATTACK on the amazing business that I have built, and the FAKE Bergdorf’s "case." PROUD TO BE AN AMERICAN!," Trump wrote in a post on his social media site Truth Social. 

BIDEN CAMP DISMISSES TRUMP IMMUNITY RULING: 'DOESN'T CHANGE THE FACTS'

The former president was charged in August 2023 by Special Counsel Jack Smith with conspiring to overturn the results of his election loss to President Biden in the run-up to the Jan. 6, 2021, riot at the U.S. Capitol. 

Trump has denied doing anything wrong and has said this prosecution and three others are politically motivated to try to keep him from returning to the White House.

Trump shared his reaction to the Supreme Court's ruling on his presidential immunity case, saying it's a "big win for our constitution and democracy," according to his Truth Social page. 

"THE SUPREME COURT DECISION IS A MUCH MORE POWERFUL ONE THAN SOME HAD EXPECTED IT TO BE. IT IS BRILLIANTLY WRITTEN AND WISE, AND CLEARS THE STENCH FROM THE BIDEN TRIALS AND HOAXES, ALL OF THEM, THAT HAVE BEEN USED AS AN UNFAIR ATTACK ON CROOKED JOE BIDEN’S POLITICAL OPPONENT, ME. MANY OF THESE FAKE CASES WILL NOW DISAPPEAR, OR WITHER INTO OBSCURITY. GOD BLESS AMERICA!" Trump posted. 

Fox News Digital's Brooke Singman and Brianna Herlihy contributed to this report.