A year ago, in the aftermath of his near-miss Senate run, O’Rourke was already viewed as a top-tier presidential contender, improbably polling third, behind former Vice President Joe Biden and Sen. Bernie Sanders.

Former President Barack Obama was publicly drawing comparisons between the former Texas congressman and himself, while former Obama aides were privately encouraging young operatives to move to O’Rourke’s hometown, El Paso, to get in early on the campaign. The media would soon encamp on the sidewalks there.

Rival candidates feared O’Rourke would swamp them with his donor list, after raising more than $80 million in his near-miss Senate campaign against Ted Cruz.

Dan Pfeiffer, the former Obama communications director, said in an op-ed for Crooked Media at the time that he had “never seen a Senate candidate — including Obama in 2004 — inspire the sort of enthusiasm that Beto did in his race.” And when O’Rourke announced his candidacy in March, spinning through crowds in southeastern Iowa, then driving east to New Hampshire, it appeared he might in the presidential race, as well.

In the first day of his campaign, he raised a staggering $6.1 million.

Beto O'Rourke speaks to volunteer Charlie Jordan as she tries to hold back tears after O'Rourke announced he was dropping out of the presidential race. | Joshua Lott/Getty Images

Then it evaporated.

The proximate cause of O’Rourke’s fall was not in the unorthodox things he did. His meandering, solo road trip through the Southwest, the livestreaming of his dentist visit, even the infamous “born to be in it” Vanity Fair cover — which he later said he regretted — all happened before O’Rourke cratered.

Rather, it was everything he didn’t do — rendering him an object lesson in the familiar limits of charisma, the liability of high expectations and the importance of organization.

Or, as O’Rourke might say, of having one’s “shit” together.

For too long — and irreparably — he did not.

While other candidates were assembling campaign staffs and volunteer armies in early nominating states, O’Rourke lacked the infrastructure necessary to organize his own supporters. Lawmakers and major Democratic donors could not get calls returned. When the campaign’s skeletal staff promised to reach out, it sometimes forgot.

The signs of disorder were startling. He announced his candidacy before hiring a campaign manager. Two senior officials who had worked on O’Rourke’s Senate run and on Sanders’ 2016 presidential campaign, Becky Bond and Zack Malitz, abruptly left. On the eve of his campaign announcement, O’Rourke was forced to personally apologize to at least one prominent Iowa Democrat for his lack of organization, according to a source familiar with the conversation.

O’Rourke’s initial handling of the media was just as clumsy. He alienated reporters by refusing to provide basic information about his schedule — including, for many outlets, the location of his campaign’s first public event. He later acknowledged he needed to do a “better job” reaching a national audience.

But at first, he believed he didn’t have to — that based on the success of his Senate campaign’s social media effort, he could largely bypass the traditional press, two people familiar with the campaign said.

It was a miscalculation, and O’Rourke was punished for it. When he hesitated or demurred — as he did frequently on policy questions early in the campaign — he was cast as a lightweight in a field populated by senators and a former vice president.

“I heard the way you ingratiate yourself to voters is to stand on things, so I found this park bench here,” Pete Buttigieg, the mayor of South Bend, Ind., joked at an event in New Hampshire this spring, referring to TV coverage of O’Rourke standing on tables and countertops while speaking at events.

That gentle ribbing gnawed at O’Rourke’s supporters. They often contrasted O’Rourke’s trajectory with that of Buttigieg, another young, relatively inexperienced politician who is currently surging in the presidential race.

Entering the contest with less attention, Buttigieg was still introducing himself to the electorate when O’Rourke was getting knocked down. If initial expectations had not been so high for O’Rourke, he might never have become the serious contender he briefly was. But he also might not have fallen so hard.

By summer, Jen O’Malley Dillon, O'Rourke's highly-regarded campaign manager, had built out his political and policy operation, recruiting top talent to El Paso. O’Rourke had set forth a swath of detailed plans on issues ranging from climate change to immigration and government reform. And following the shooting in El Paso in August, his controversial proposal of a mandatory buyback of assault weapons helped push the nation’s gun control debate to the left.

But it was too late. O'Rourke's fundraising had fallen off almost immediately after he entered the race, and he never recovered. He performed poorly in the first primary debate, appearing shaken when a fellow Texan, Julián Castro, tore into him over his opposition to decriminalizing border crossings. O’Rourke disliked debates and preparing for them, and he felt after the encounter with Castro that he had been stilted and over-prepared, according to a source familiar with the campaign.

He raised just $3.6 million in the second quarter of the year, and $4.5 million in the third quarter.

By Friday, an adviser said, O’Rourke was running out of money. The campaign explored the possibility of public financing, but abandoned the idea, a campaign adviser said. Layoffs, said Aleigha Cavalier, O’Rourke’s press secretary, “were never an option” O’Rourke considered.

Instead, standing on a box in a park by the Des Moines River, O’Rourke told a small group of supporters that he could “clearly see at this point that we do not have the means to pursue this campaign successfully.”

It didn’t matter that he had a policy platform or a campaign infrastructure, or that he had largely stabilized his relationship with the press. By the time he did, O’Rourke was no longer a top-tier competitor. Democratic voters were not taking him seriously anymore.

In a sign of the campaign’s frustration, Rob Flaherty, O’Rourke’s digital director, posted a photograph on Twitter of a t-shirt he said the campaign was “going to put out but didn’t.”

Beto O'Rourke hugs a supporter after announcing he was dropping out of the presidential race. | Joshua Lott/Getty Images

It read, in all caps: “HE WASN’T STREAMING HIS DENTIST APPOINTMENT HE WAS SHARING THE HYGIENIST’S STORY.”

Before O’Rourke’s arrival at the park on Friday, his staff set out a box with the words “soap” and “Beto 2020” stamped on it in black lettering.

A woman craning for a photograph of the platform said, “Where he began is where he’s ending.”

A woman next to her, noting that O’Rourke is only 47, hinted he might run again.

O’Rourke suggested in an interview in September that he will not. “I cannot fathom a scenario where I would run for public office again if I’m not the nominee,” he said.

On Friday, speaking in a sweater, he told his supporters, “This has been the honor of my lifetime.”

Then he lingered for more than an hour, hugging supporters and staffers in the dark across the street from the convention center where the other, still-running candidates assembled for the massive state party event known as the Liberty & Justice dinner.

Embracing tearful supporters, O’Rourke described his campaign as a “transcendent” experience. “As tough as this day is,” he reassured one man, “there’s just something beautiful that’s going to stay with me, some kind of optimism I have about where the country’s going because of all the people I’ve met.”

If he couldn’t answer why that wasn’t enough, it was because what O’Rourke cherished about running for office — the crowds, the road, the exchange of ideas, even as his crowds thinned — rarely is.

After O’Rourke left, Norm Sterzenbach, the veteran strategist who marshaled O’Rourke’s operation in Iowa, stayed behind, removing campaign signs. When a staffer told him that a drill to disassemble large, wooden lettering at the edge of the park wasn’t working, Sterzenbach pulled one down with his hand.

“Gravity,” he told the staffer. “One of the most powerful forces in nature.”

Alex Thompson contributed to this report.