The decision came weeks after a disastrous debate performance triggered a wave of panic among fellow Democrats.

Then, in the aftermath of an assassination attempt that helped elevate Donald Trump to hero status among his already fervent base, calls among Democrats for Biden to step aside reached a breaking point.

I'm not sure the word unprecedented really does this justice.

We have just never seen a political story like this.

Several stark moments during Biden's debate showdown with Trump on June 27th brought his age and mental acuity into question, even among his staunchest supporters.

Dealing with everything we have to do with, look, if we finally beat Medicare.

A few members of Congress came out pretty early after the debate performance.

Then the Biden folks seemed to be trying to manage it.

Biden did a bunch of calls with donors.

He did some events.

He did an interview on ABC.

And if you stay in and Trump is elected and everything you're warning about comes to pass, how will you feel in January?

I feel as long as I gave it my all and I did the goodest job as I know I can do.

That's what this is about.

The president's struggles continued in the weeks following the debate.

Ladies and gentlemen, President Putin.

President Putin.

He's going to beat President Putin.

President Zelensky.

I wouldn't have picked Vice President Trump to be vice president.

After the debate went so badly, he had no margin for error at those events.

Democrats and voters who were already worried about him and saw those appearances just did not find them reassuring enough to go forward.

One by one, top Democrats went public with their concerns.

The unrest also spread to the party's donors, including calls for Biden to step aside from Netflix founder Reed Hastings and actor George Clooney.

The president forcefully pushed back on questions about his viability as a candidate in a closely watched press conference on July 11th.

I'm not in this for my legacy.

I'm in this to complete the job I started.

Then, on July 13th, the assassination attempt on Donald Trump galvanized his supporters.

An energized GOP unified around the former president at the Republican National Convention the following week.

The contrast you saw was a very united Republican Party at a moment when the Democrats were very divided and struggling.

Meanwhile, in Las Vegas, The president has been at many events, as we all know, and he just tested positive for COVID.

Arriving in Delaware to self-isolate, Biden appeared to struggle to get into a car after disembarking from Air Force One.

Democrat leaders, fearing steep losses in down-ballot congressional races, ramped up their efforts to oust Biden from the race.

Senate Majority Leader Chuck Schumer and House Minority Leader Hakeem Jeffries pushed for Democratic officials to delay formally naming Biden as the party's nominee.

People familiar with the matter told The Wall Street Journal.

Representative Adam Schiff became one of the highest-profile Democrats to publicly call on Biden to bow out.

Good afternoon.

I'm not sure there was anything he could do after that debate.

People were so shocked and scared.

And the bottom just fell out very quickly on the money.

And people couldn't unsee it.

They saw what happened, and they were just so worried that something like that would happen again and cost them not just the White House, but also Congress.

Concerns about Biden's age and mental acuity are not new.

They came up when he ran for president against Trump in 2019 at age 76.

You just said two minutes ago that they would have to buy in.

You said they would have to buy in.

If she qualifies for Medicaid, she automatically would be in for it.

During Biden's years in the White House, his staff largely shielded the president from the media.

Compared to recent presidents, President Biden had done less interviews.

He had done less lengthy press conferences.

And there have been just less opportunities for the press to question him in a lengthy format.

His age came under fresh scrutiny in February, when the special counsel investigating Biden's handling of classified documents released a report in which he's described as a sympathetic, well-meaning elderly man with a poor memory.

My memory is not good.

My memory is fine.

My memory, take a look at what I've done since I've become president.

None of you thought I could pass any of the things I got passed.

Less than a month before the June 27th debate, The Wall Street Journal reported, based on signs of slipping.

Democrats are looking not just at the presidency, but also whether they can hold the Senate and whether they could win back the House.

The Republicans are very energized.

They're very united.

They're very clearly behind their candidate.

And they're heading into the fall election season feeling really confident.

And Democrats now have to go through a really tough thing.

And maybe they come out the other side of that really unified, that they can get folks on board, that they can also be energized.

But that's more of an open question right now.