President Joe Biden blamed his globetrotting ahead of Thursday's disastrous debate for his poor performance.

The 81-year-old president made the concession during a fundraiser in the ritzy D.C. suburb of McLean, Virginia Tuesday night.

He told the crowd he 'wasn't very smart' for 'traveling around the world a couple times' before his showdown with presumptive Republican nominee, former President Donald Trump.

'I decided to travel around the world a couple of times … shortly before the debate …I didn’t listen to my staff … and then I almost fell asleep on stage,' the president said

He added, 'It's not an excuse but an explanation.'

Biden had an entire week holed up at Camp David to prep for the debate after spending the Juneteenth holiday at Rehoboth Beach.

Before that he did back-to-back trips to France to mark the D-Day anniversary and then to Italy for the G7.

The New York Times reported Tuesday that Biden was so drained from the jetsetting that advisers cut debate prep short by two days - in order to fit in the beach trip.

And then while at the presidential retreat, debate prep didn't start before 11 a.m. and Biden was given time each day in the afternoon to take a nap.

The fundraiser was scheduled after press secretary Karine Jean-Pierre was forced to give her own expanation about the president's poor debate performance from the White House podium. 

The tense exchanges show how the issue of a declining president will overshadow the rest of this year's election, as nervous Democrats begin openly calling for Biden to step aside.

'We're not taking away from what you all saw or what the American people saw,' said Karine Jean-Pierre. 

'We understand it was a bad night. It is not uncommon for incumbents to have a bad night on their first debate, and we are going to continue to do the work that we have been doing on behalf of the American people.'

Her answers were greeted with incredulity in the White House briefing room as she explained that the president was simply suffering from a cold and had no plans to step aside.

And she was peppered with follow-up questions, asking whether he had taken cold medication before the debate (no, she said) or whether there was something even more serious wrong with him.

At one point she was asked whether he was 'disabled.' 

Another reporter asked: 'I think the American people need to get a yes or no answer on this: Does President Biden, at 81 years old, have Alzheimer's, any form of dementia or degenerative illness that caused these sorts of lapses?'

Jean-Pierre answered: 'It's a no. And I hope you're asking the other guy the same exact question.'

The problem for the White House and the Biden campaign is that Trump emerged as the clear winner of the debate.

Biden looked every one of 81 years, as his answers ground to a halt or rambled into bizarre non sequiturs.

He was unable to challenge Trump's exaggerations and falsehoods, and at the end of the 90 minutes was helped off stage by his wife. 

The poor performance has dominated news headlines ever since, triggering panic among Democratic donors who fear his campaign is sleepwalking into disaster.

Questions in the briefing room about what sort of shape Biden will be in at the end of a second term and about dementia will not help.

Jean-Pierre did her best to draw a line under the debate. She painted a picture of a busy president getting on with the job, traveling to Wisconsin later in the week, sitting down for an interview with ABC News' George Stephanopoulos, and hosting a solo press conference next week when NATO leaders are in town. 

She also confirmed he was holding a virtual meeting with Democratic governors, but would not answer questions about whether it was designed to offer reassurances. 

'We want to turn the page on this, and we want to turn the page for the American people as well, because we know that they need to see him out there,' she said.

Whether it will be enough to quell growing concern among donors and strategists is another matter. 

Several told DailyMail.com they were amazed that the president had gone to ground during the weekend, rather than launching a fightback immediately. 

On Tuesday, private chatter exploded into the open as the first elected Democrats went public with calls for Biden to drop out of the race. 

Rep. Lloyd Doggett of Texas became the first Democratic member of Congress to call for Biden to step down. 

'My decision to make these strong reservations public is not done lightly nor does it in any way diminish my respect for all that President Biden has achieved,' he said.

'Recognizing that, unlike Trump, President Biden's first commitment has always been to our country, not himself, I am hopeful that he will make the painful and difficult decision to withdraw. I respectfully call on him to do so.'