With barely 10 minutes warning, a press staffer yelled at shocked journalists and hustled them to the White House Rose Garden just before noon on Wednesday to witness an abrupt moment of history.

The ceremonial venue, the stolen glances at a teleprompter and word that President Barack Obama and Vice President Joe Biden would appear told the reporters all they needed to know.

Biden used the space reserved for the most ornate and somber presidential theater to announce he wasn’t running for President, suddenly ending the feverish speculation that increasingly consumed Washington.

This account of the swift and poignant end of Biden’s presidential prospects is based on interviews with multiple friends and aides of the Vice President. It illustrates the excruciating process he went through over the past several months to determine whether he could mount a winning campaign after the death of his eldest son this summer and take on front-runner Hillary Clinton. And it shows that for all the groundwork Biden appeared to be laying, his decision not to run seemed to come suddenly.

Biden told the gathered reporters on Wednesday that he had already warned — in a soul-bearing interview with Stephen Colbert’s show — that his family’s grief over the loss of Beau Biden could cause his window for a credible White House run to close.

“I’ve concluded it has closed,” Biden said simply before a clutch of senior administration officials including national security advisor Susan Rice and White House Chief of Staff Denis McDonough, who were hurriedly rounded up to witness Biden end his presidential dreams.

Broad outreach

But Biden’s broad outreach to a lifetime of political allies and associates in recent weeks left many convinced he would indeed mount an unlikely bid to become the oldest man ever elected president. Just this week, Biden reinforced that impression by staking out political ground, jabbing Clinton and sharpening rhetoric that seemed to augur a run.

A senior Biden aide confided that the vice president only made his final decision on Tuesday evening as the clock raced towards filing deadlines and milestones on the road to early nominating contests that he could no longer ignore.

Ultimately, according a source familiar with Biden’s thinking, the Vice President became hung up on a couple of key points.

First: The emotional marker Biden laid in his Colbert appearance — one of the most heart-rending and honest glimpses into a politician’s pscyhe in years — was so heavy that it was tough to argue his family was ready for a run.

“It’s kind of hard to pivot out of that,” the source said.

Joe Biden: Images from a political life
Joe Biden

And Biden also took the warnings of James Clyburn, the South Carolina congressman he deeply respects, who told the Huffington Post this week that he would not advise him to get into the race.

Given the strength of Clinton and surprise endurance of Bernie Sanders in Iowa and New Hampshire, the Palmetto State would be the place where Biden would plant his flag in early states to grab political momentum.

In a way, the relentless media coverage of a potential Biden run for president seemed to outpace the veteran politician’s own deliberations, which did not only center on his grieving family’s emotional health.

‘He wanted to run’

“I don’t think he ever got to the point where he would justify the risk of doing this,” said the source familiar with Biden’s thinking. “It’s clear he wanted to run, as we all know, but the reality of it was too tough. He knows what the realities of a campaign demands.”

Still, another source close to Biden said that the Vice President enjoyed the process of working through his options immensely, and in a way, his deliberations turned into therapy as he recovered from his loss. But some of the media coverage, which he read voraciously, aggravated him and he was especially infuriated by reports that he was not genuinely taking a serious look at a run.

When it came down to it, however, the political omens were always daunting.

Biden well understood Clinton’s vigor and toughness, the narrowness of his own potential path to the nomination — and the fact that presidential campaigns just can’t be built in a couple of months.

“This was a hard decision for him,” a senior administration official said, stressing that Biden only made one firm decision — not to run for president — and did not vacillate between jumping in and staying out, possibly in an attempt to debunk “Hamlet on the Potomac” scenarios which suggested a hesitating Vice President was paralyzed by indecision.

Some days, Biden felt bullish on the possibilities and on others he didn’t, a close associate said, comparing the vice president’s mood to high and low tide.

The senior official said that Biden concluded there was simply not sufficient time left to raise enough money, to establish a political organization and to do what the vice president loves and does best, wooing crowds with his zeal for retail politics.

Not a mirage

Still, the potential campaign was not a mirage. The vice president had asked advisers to consider likely scenarios should he get into the race as well as to make contact with operatives who would be prepared to staff up a campaign.

That would explain why so many people honestly believed that Biden was set on an opposite course to the one he adopted in the Rose Garden.

One person fooled was Rep. Brendan Boyle who had previously tweeted that he was sure Biden would make the race.

“I’m very surprised. Clearly something changed from this weekend till today. I have new found sympathy for reporters!” Boyle said after Biden’s speech.

There’s a certain irony to the fact that Biden, one of the most notoriously loose-lipped men in Washington, managed to keep his thinking so locked down.

In fact, the vice president had been surprised that his 2016 hopes ever inflated. He never seriously considered a third presidential bid until after the death of Beau, who reportedly pleaded with his father to make one final run for president.

“The whole thing kind of caught him off guard from the start,” said the source familiar with Biden’s thinking.

At the same time, Clinton’s slump in the polls over the summer, as she struggled to contain the furor over her personal email use during her tenure as secretary of state, raised the specter that the Democratic Party’s vaunted front-runner could implode — and thus open the way for Biden as Obama’s heir apparent.

“That turned what was always perceived as a far-fetched idea into a possibility,” the source said.

Clinton called Biden after his speech, her communications director Jennifer Palmieri told CNN. But there was no sense in the vice president’s remarks that he was yet ready to fall into line and endorse her.

There was a tantalizing glimpse on Wednesday of the campaign that might have been.

With a wistful Obama at his side, Biden mounted a fierce defense of the administration’s legacy and left no doubt that it should anchor the 2016 presidential campaign.

“I believe that President Obama has led this nation from crisis to recovery, and we’re now on the cusp of resurgence,” said Biden.

“I’m proud to have played a part in that. This party, our nation, will be making a tragic mistake if we walk away or attempt to undo the Obama legacy,” warning that Democrats must battle for the middle class and combat what he said were “unsustainable” levels of economic inequality.

Biden’s call for free college education, for the wealthy to pay more in taxes, and warning that America must avoid open ended military excursions abroad hinted at a narrative in Obama’s own image.

And the vice president had a veiled warning for Clinton, again implicitly rebuking her for her remark in the Democratic debate on CNN last week that Republicans were her enemies.

Partisan politics, he cautioned, were ripping the United States apart. “It’s mean spirited, it’s petty and it’s gone on for much too long.”

Affection for Biden

Though many in Obama’s White House feared the consequences of a Biden presidential campaign, both for his own legacy and their hopes that Clinton can secure a political inheritance from Obama, there is no doubting the affection in which the vice president is held.

After sometimes becoming irritated by Biden during his 2008 run, and the vice president’s penchant from gaffes and volcanic verbosity, Obama came to deeply trust and appreciate his loyal subordinate. That bond burst into the open when Obama placed a kiss on Biden’s cheek after delivering a moving eulogy at Beau Biden’s funeral this summer.

WATCH: A peek at Joe Biden’s past presidential campaigns

So there will be some relief in the West Wing that Biden will not face the indiginities of what could have been a futile White House run.

And after a career bracketed by tragedy — after the death of his wife and infant daughter after he was elected to the Senate in 1972 — and the loss of Beau this year, some will take solace that Biden has now arrived at some inner peace.

He said he will fill the inevitable void left by the end of his White House apirations with a new challenge — what he called a “moonshot” to find a cure for cancer — in honor of his son, while putting the capstone on the Obama agenda.

“Now, all he has to do is find the energy and strength to do it,” a person close to Biden said. “And I believe he will.”

As reported by CNN