NEW YORK – Mike Bloomberg awoke early on that crisp and cloudless Tuesday and walked from his East Side mansion to his neighborhood polling place, where he saw his name on an election ballot for the first time, as a Republican candidate for mayor.

It was Sept. 11, 2001, primary day, and Bloomberg was in the thick of trying to reinvent himself as the face of America’s largest city, an aspiration many New Yorkers regarded as audacious, if not laughable, for a little-known billionaire CEO.

After voting, Bloomberg walked downtown to his campaign headquarters, where he drank coffee and scanned the newspapers at his desk, a cubicle among rows of cubicles occupied by strategists and policy advisers.

Then someone told him that an airplane had slammed into the World Trade Center.

On television, a newscaster wondered whether technical problems had disrupted communications between air traffic control and the plane.

“Bulls—,” Bloomberg said.

As a licensed pilot, he knew that the morning’s clear skies were perfect for flying and it was unthinkable a plane would travel at such a low altitude. ” ‘You don’t need radar or air traffic control to tell you where the World Trade Center is,’ ” Bill Cunningham, an adviser, recalled Bloomberg saying. “He knew something really bad was going on.”

At 9:03 a.m., when the second plane hit the South Tower, Bloomberg’s fears were validated.

In that moment of confused panic, Bloomberg displayed the instincts that propelled his evolution from Wall Street trader to technology entrepreneur to founder of a multibillion-dollar media empire with offices around the world, his name over each entrance.

It was that same self-assurance – some would say arrogance – that drove Bloomberg, then 59, with a crooked smile and no discernible trace of charisma, to surrender the cloistered life of a private citizen for the hothouse of New York politics.

Yet what Bloomberg did not know in that moment – what no one could have known – is that the deadliest foreign attack on American soil would fuel his unlikely rise as New York’s mayor and become a foundation for his race for the White House.

As he stakes his presidential campaign on capturing a windfall of Super Tuesday delegates, Bloomberg invokes his stewardship of post-9/11 New York to cast himself as the competent, even-keeled antidote to President Trump’s turbulent reign.

“We began to write a comeback story,” Bloomberg tells audiences, recalling that he took over a city “in tatters” after winning an election that “almost no one” – not even his mother, he often notes – “thought I had a chance.”

At the same time, Bloomberg, an engineer by training, is suspicious of analyses devoid of data and reluctant to attribute his political birth entirely to 9/11.

“I don’t know how I got elected or why I got elected other than more people voted for me,” he said this month in Detroit during a brief interview between campaign stops. “But I don’t know why they voted for me.”

Bloomberg’s 12 years at City Hall lifted him to newfound prominence and spanned the rebirth of Lower Manhattan, the rise of the new World Trade Center and the opening of the 9/11 Memorial.

Yet, in 2001, as he aspired to succeed Republican Mayor Rudy Giuliani, he was largely unknown beyond Wall Street and the exclusive dinner parties and charity galas he frequented.

“Who is Bloomberg?” Ester Fuchs, then a Barnard College political science professor, asked when his pollster suggested she meet with him.

By the morning of Sept. 11, polls showed Bloomberg would win the GOP primary. But his prospects in November remained dim in a city where Democrats outnumbered Republicans 5 to 1.

After the twin towers collapsed and Gov. George Pataki postponed the primary, Bloomberg learned that the brother of a campaign staffer was missing and that three of his company’s employees had been at a conference on the 106th floor of the North Tower.

“I’m SCARED,” Peter Alderman, 25, a Bloomberg employee, wrote in a 9:07 a.m. email to his sister from Windows on the World, where he was trapped. “THERE IS A lot OF SMOKE.”

Alderman’s parents were in France that day celebrating his father’s 60th birthday when their phone rang.

“It’s Mike Bloomberg,” he said.

As the company’s boss, he felt it was his responsibility to tell the Aldermans what he knew about their son. A team of his employees had been assigned to call hospitals around the city about Peter. His whereabouts remained unknown.

” ‘We’re searching for him,’ ” Elizabeth Alderman, Peter’s mother, recalled Bloomberg saying.

She struggled to remain hopeful. The billionaire was measured and matter-of-fact.

He promised to call back.

– – –

Rudy Giuliani wanted to sound encouraging as he listened to Bloomberg talk of his ambition to follow him as mayor. They were sitting in the living room at Gracie Mansion, the mayor’s official residence, in the spring of 2001, a few months before Bloomberg entered the race.

“What do you want to make a change for?” Giuliani asked.

Bloomberg said only four jobs piqued his interest: United Nations secretary general, World Bank president, president of the United States and the seat opening at City Hall when Giuliani completed his term.

Bloomberg impressed the mayor with his knowledge of city policies and his willingness to spend millions of his own fortune on the campaign. But Giuliani told Bloomberg what he told any Republican running in his city. ” ‘Republicans can’t win in New York unless there’s a disaster,’ ” Giuliani recalled warning. “Or let’s say, things are really bad.”

Giuliani listed the crises that had swept Republicans Fiorello La Guardia and John Lindsay into office. In his own case, Giuliani cited two riots and a soaring murder rate that presaged his victory over the Democratic incumbent David Dinkins.

” ‘Yes, but times change,’ ” Bloomberg said, recalled Giuliani, who thought the businessman was “very sure of himself. I was more impressed than I thought I’d be. I came away thinking he’d be a good mayor; too bad it’s a Democratic city.”

A Democrat until just before the mayor’s race, Bloomberg became a Republican because he couldn’t win the Democratic nomination against two well-known city pols, Fernando Ferrer and Mark Green, the eventual nominee.

His party switch was emblematic of the pragmatism and ambition that had infused Bloomberg since his upbringing in Medford, Massachusetts. – the son of a bookkeeper and a homemaker – where he collected enough merit badges to become an Eagle Scout at age 12.

“Suck it up and just get on with it!” was how his parents taught him to deal with adversity, Bloomberg told a biographer. “Don’t let bad things that happen to you stop you.”

At Salomon Brothers, where he earned $9,000 a year after graduating from Johns Hopkins University and Harvard Business School, his first job was counting billions of dollars in securities inside a sweltering vault known as “the Cage.” To keep cool, he stripped to his underwear and drank beer.

Salomon’s culture was a blend of Brooks Brothers suits and loading-dock profanity. Bloomberg gained a reputation as a hard-driving boss who on occasion would throw a phone if the conversation wasn’t going his way. His underlings teased that his edge was unbefitting “someone born on Valentine’s Day,” said Richard Levy, a trader who worked for Bloomberg.

When Levy had to miss work on a frenetic trading day because his grandfather died, Bloomberg asked whether he could delay the funeral, even though Jewish law requires burial within 24 hours. “Michael, you should know better,” Levy recalled telling him. Bloomberg, who is Jewish, apologized.

After Salomon merged with another company in 1981, the firm dismissed Bloomberg, though not without a $10 million payout he used to create the now-famous computer terminal that carries his name. Over the next two decades, Bloomberg LP grew to 8,000 employees in more than 100 countries and annual earnings exceeding $2 billion.

A rising star in business circles, Bloomberg in 1993 invited a New York magazine reporter to his office, apparently unconcerned about how his banter might come off. At one point, he commented on the attractiveness of an employee, saying, “She is the reason all the young programmers come in early and stay late.” At another, he tossed Cheez-Its into a trash can and joked, “I could play for the Knicks if I ever grew up to be seven foot one and black.”

Entering his 50s, Bloomberg divorced his wife, Susan, the mother of their two daughters, and became a bachelor about town. His dates with age-appropriate stars such as Marisa Berenson and Diana Ross inspired the New York Post to tag him the “anti-bimbo billionaire.” Bloomberg hosted parties with the likes of Harvey Weinstein, the now-disgraced Hollywood producer, and Tina Brown, the then-prominent magazine editor. In London, he threw a bash called “Seven Deadly Sins,” featuring drag queens, massage tables and an oversize bed sheathed in purple satin.

“Money, ain’t it gorgeous?” shouted performers waving cash.

– – –

Bloomberg and Alfred Sommer, a prominent ophthalmologist he knew through their affiliation with Hopkins, were eating steaks one night when the businessman asked a surprising question.

“What do you think about me running for mayor?”

“Why would you want to do that?” Sommer replied. “Why would anyone want to do that?”

By then, Bloomberg had palatial homes in Manhattan, London and Bermuda, and enough money that he could afford to donate tens of millions to various causes. He wanted a new challenge and public service appealed to his inner Eagle Scout.

As he contemplated a different path, Bloomberg consulted a long list of political operatives, including Bill Cunningham, a former adviser to Sen. Daniel Patrick Moynihan, D-N.Y.

“You have any idea what guys like me do to guys like you?” Cunningham recalled asking. He warned that Bloomberg’s wealth would be a bull’s eye for opponents lampooning him as an out-of-touch oligarch.

“That’s what’s wrong with politics,” Bloomberg snapped. He insisted that he was more than his money and that he had the credentials to govern.

Cunningham joined a growing cast of strategists around Bloomberg, a troupe including New York’s preeminent political guru, David Garth, who had steered Lindsay, Democrat Ed Koch and Giuliani to mayoral victories.

Their new boss, they learned, had no patience for chitchat or navel-gazing. He could be blunt, profane and biting.

“How do you live with her?” Bloomberg said when meeting the husband of Ester Fuchs, by then a policy adviser, who was flabbergasted until she saw the billionaire’s smirk.

He also had a lot to learn about New York politics.

When pollster Frank Luntz told him that winning would be difficult, Bloomberg said, “The only reason I’m talking to you is for you to make it less difficult.”

“There were no pleasantries,” Luntz said. “Mike is business: To him, I was a political hack, and he didn’t want to fake it.”

One adviser’s assignment was to make flashcards to quiz him on New York minutiae like “How many miles is the transit system?” “Who is the City Council speaker?” and “What is rent control?”

Bloomberg knew that he needed Hispanic votes, which is why he hired a Spanish teacher, Juan Carlos Ayarza. At one point, Ayarza accompanied Bloomberg on a week-long business trip to Europe and Asia, tutoring him only when they were airborne in his jet.

“Here’s your money. Go tour,” Bloomberg said when they landed, Ayarza recalled.

His political operatives had to teach him the basics of campaigning.

“Ever march in a parade before?” Ed Skyler, his press secretary, asked as they set off for the Israeli Day celebration.

“Maybe the Boy Scouts,” Bloomberg said, an answer that compelled his aide to remind him that when encountering a television camera “wave and smile like you’re in a sold-out stadium.”

On the campaign trail, Bloomberg was The Unnatural, dressed in polo shirts and tasseled loafers, his nasal voice an odd blend of Bahston and New Yawk.

“A friend of mine just bought the Jets,” he said cheerfully after meeting a kid wearing a Baltimore Ravens T-shirt, an exchange captured by a documentary filmmaker. Another voter, grilling hot dogs, is shown asking Bloomberg for a loan of “half-a-mill” to renovate his house.

“I know Michael’s got it,” the man says as Bloomberg chuckles and moves on.

As he announced his candidacy at a Queens seniors center, Bloomberg boasted that his company’s “customers think we walk on water – and we do. I can do that for the city.”

“Not Even Close to Being Ready,” a Daily News headline declared the next day.

As summer passed, Bloomberg poured millions into TV ads and climbed in polls that once showed him losing by more than 2 to 1. George Arzt, Koch’s former adviser, had doubted that working-class voters would embrace a billionaire. But Arzt found himself beginning to think otherwise as he left a Mets game one night and saw dozens of Bloomberg volunteers handing out “Mike for Mayor” bubble gum.

“Wow, I never saw this in a campaign,” he thought.

On the eve of the primary, Bloomberg fended off attacks over off-color wisecracks he had purportedly made a decade earlier, all of them collected by a former employee in a booklet called the “Portable Bloomberg.” “Make the customer think he’s getting laid when he’s getting f—ed,” read the first entry.

At their final debate, Herman Badillo, his Republican primary opponent, cited the booklet as evidence that Bloomberg was unfit to be mayor.

Two days later, after the first plane struck the World Trade Center, voters were no longer paying attention.

– – –

At his headquarters, Bloomberg learned about the three company employees who had been on the 106th floor. When he reached Peter Alderman’s parents in France, he assured them that he would send his plane to fly them back to New York.

“I want you to stay calm,” he said. “We’ll call you back as soon as we know anything.”

The following day, he phoned again.

“No one survived above the 91st floor,” Bloomberg told the Aldermans. “I wish I could tell you better news.”

Elizabeth Alderman felt her knees buckle. She began to weep and dropped to the floor.

His pilot would be in touch, Bloomberg promised. A few days later, a limousine was waiting when the Aldermans landed in New York.

The next morning, their doorbell rang. Bloomberg was on their front step, alone.

He had come to say how sorry he was about their son.

Twenty-four hours after the attack, Bloomberg and his advisers convened at campaign headquarters. Outside, the midtown streets were barren as the city and country awakened to fears of new threats and an uncertain future.

“What do we do now?” Bloomberg asked his team.

His campaign commercials would halt, and he would make no immediate public appearances. But larger questions remained: How would they respond to the catastrophe once the campaign resumed?

Before Sept. 11, Bloomberg struggled to sell voters on the merits of a political outsider with a business background. But Lower Manhattan was now defined by a huge crater, and voters feared that corporations would flee and the city’s economy would tank. Bloomberg’s advisers saw an opportunity. Their candidate’s executive background was now an asset.

“It became pretty clear once the shock of the event passed that the qualifications for the job had changed,” Skyler said. “Mike’s experience became a lot more relevant.”

A day after winning the rescheduled Republican primary, a gaggle of television crews followed Bloomberg to the Brooklyn Heights Promenade, which overlooks the East River and has panoramic views of Manhattan’s skyline.

“What we have going forward here is a different city,” he said after pausing to gaze across the water where the twin towers had stood. “And the mayor’s job is different than it was before.”

While Bloomberg still trailed by 16 points in the polls, the gap narrowed as Green, his opponent, made missteps and the Democrats were consumed by racially charged infighting.

Yet Bloomberg’s greatest advantage was the endorsement he received from Giuliani, whose post-9/11 performance inspired standing ovations wherever he went. “Mike will build on what we’ve accomplished,” Giuliani said in an ad that aired ceaselessly in the campaign’s final hours.

On the election’s eve, as he circled the city to rally voters, Bloomberg received a late-night call from Harvey Weinstein, who somehow thought it essential to let him know that he had abandoned Green and was supporting him.

” ‘Call the newspapers and tell them!’ ” Weinstein urged, Bloomberg recalled. “And I said, ‘Harvey, it’s 11 or 12 o’clock, f— you! The newspapers are on the streets already. I’m not going to call them.’ “

On Election Day, Bloomberg told his mother that he might lose but that the results would be close enough she wouldn’t be embarrassed. Past midnight, his campaign manager, Kevin Sheekey, put away the concession speech he had drafted. After spending a record $70 million of his own money, Bloomberg had won by 35,000 votes – or less than 3 percent.

“New York is alive and well and open for business!” the mayor-elect told supporters.

But the city remained in a suspended state of anguish. As the first anniversary of the attack approached, Bloomberg’s staff assembled a list of survivors of the 400 firefighters and police officers who were killed.

He would call each one.

Sometimes, the person on the other end was composed and the call began and ended easily. Sometimes, the person was crying and Bloomberg could hear children playing in the background.

After a few minutes, the new mayor hung up and went on to the next call.

– – –

On the 10th anniversary of the attacks, as bagpipers played and New York paused to reflect, Bloomberg presided over the opening of the 9/11 Memorial, a milestone that drew President Barack Obama and more than 10,000 relatives of the dead.

Soaring over the ceremony was the rising symbol of New York’s recovery – 82 of the 104 stories that would become the new World Trade Center.

“We can never un-see what happened here,” Bloomberg told the crowd assembled alongside two memorial pools tracing the footprints of the fallen towers. Etched in bronze parapets were the nearly 3,000 names of the dead, including that of Peter Alderman.

Over the years, Bloomberg had prodded the city to move past its collective grief. Giuliani had envisioned Ground Zero as a 16-acre memorial. Bloomberg wanted a smaller memorial and pushed for new offices and schools. He warned of turning downtown into a “cemetery.”

When he spoke to relatives of the dead still in the throes of grief, Bloomberg felt the urge to say, “Suck it up,” as his parents had taught him.

“I thought to myself, ‘It’s tragic but you’ve got to take care of your kids,’ ” he said. “You don’t want to be crying. You want to be talking about the future – ‘What can I do to help your kids?’ ‘What can I do to help you?’ – rather than look back. Looking back isn’t going to help.”

On the 10th anniversary, Bloomberg told a reporter that he did not want to be “remembered in terms of 9/11. I want the public to remember someone was there – not even knowing who they were. That they built the right thing. That they did the right thing.”

Three years later, the 9/11 Memorial Museum opened, a subterranean time capsule of that morning, the horror memorialized in photos of terrified bystanders and recordings of last voice mails from those inside the towers.

On a wall were flashing images of fliers that families taped to lampposts for the missing. “Call Mom,” one pleaded. On the bottom floor were the twisted remains of the firetruck used by the men of Ladder Company 3, a dozen of whom died.

On another wall, behind glass, was a campaign flier with the date in white letters – Tuesday, Sept. 11 – reminding voters to support a Republican on that day’s ballot.

“Mike Bloomberg,” the leaflet reads. “Don’t turn the clock back.”