By MICHAEL BARBARO JULY 22, 2016

CLEVELAND — It was Donald J. Trump’s best chance to escape his own caricature.

He did not.

After 40 years in the public eye, Mr. Trump decided on Thursday night that he was not interested in revealing himself to America with disarming tales of his upbringing, hard-earned lessons from his tumultuous career or the inner struggles masked by his outward pomposity.

In the most consequential speech of his life, delivered 401 days into his improbable run for the White House, Mr. Trump sounded much like the unreflective man who had started it with an escalator ride in the lobby of Trump Tower: He conjured up chaos and promised overnight solutions.

To an electorate that remains anxious about his demeanor, his honesty and his character, Mr. Trump offered no acknowledgment, no rebuttal, no explanation.

It was a speech that might be remembered, ultimately, as much for what it lacked as for what it contained — and for the message those absences seemed to convey: He is content with the angry voters he has won, who thunderously cheered him on here, and indifferent about wooing those he has not.

For those grasping for new signs of humility, generosity and depth, Mr. Trump offered the thinnest of reeds.

Inside the Quicken Loans Arena, a thicket of American flags behind him, he portrayed himself, over and over, as an almost messianic figure prepared to rescue the country from the ills of urban crime, illegal immigration and global terrorism.

“I alone,” he said, “can fix it.”

But Mr. Trump made no real case for his qualifications to lead the world’s largest economy and strongest military. He is, he said, a very successful man who knows how to make it all better.

Campaign speechwriters from both parties were stupefied.

“It’s a lost opportunity,” said Matt Latimer, who wrote speeches for President George W. Bush. He said he had expected Mr. Trump to plumb his personal life and career for the kind of anecdotes that would turn him, in the eyes of his doubters, from a cartoon into a flesh-and-blood human being.

“A little humanity and self-reflection,” Mr. Latimer said, “is usually very powerful in a speech.”

After reading the speech, Paul Begala, a longtime Democratic strategist and speechwriter, called the missing personal details “an enormous mistake.”

“The American people,” he said, “need to know their president’s mythic arc.”

But Mr. Trump, even at 70, seems constitutionally incapable of, or stubbornly averse to, capturing and conveying the complexities of his existence.

At every turn on Thursday night, he avoided turning a colorful and remarkable biography — populated by a volcanic father, a self-destructive brother, his own dizzying career highs and mortifying lows — into vivid, poignant storytelling.

His childhood? He learned “to respect the dignity of work,” he said.

His parents? His father liked the company of the carpenters and electricians he employed. His mother was a “great judge of character.”

His storied career? “I have had a truly great life in business,” he said. And that was that.

His wife, Melania? “Lucky to have at my side,” he said.

The most powerful convention speeches have long relied on verbal Polaroids from the past, intimate glimpses into an unseen and unknowable personal journey.

In 2012, Mitt Romney defied his reputation for stultifying oratory by extolling the romantic bond between his parents, recalling the rose his father, George, left on the pillow every morning for his wife, Lenore.

“That’s how she found out what happened on the day my father died,” Mr. Romney recalled. “She went looking for him, because that morning, there was no rose.”

The elder George Bush undertook an earnest examination of his best-known vulnerabilities, confronting his reputation for out-of-touch elitism and a lack of charisma and casting them as strengths.

“I am a quiet man,” he said in 1988, “but I hear the quiet people others don’t.”

Richard M. Nixon pleaded with voters who knew him as a bitter political outcast in 1968 to think of him instead as the boy who had grown up poor on a lemon ranch and dreamed “of faraway places where he’d like to go.”

Mr. Trump, aides said, took inspiration from that famous Nixon speech. But he left out Nixon’s uplifting message and sentimental tone, said David Gergen, an adviser to four presidents, including three Republicans.

“Trump,” he said, “threw away the glove.”

Instead, Mr. Trump projected unbending self-confidence, authority and strength. He lacerated his Democratic rival, Hillary Clinton, as thoroughly untrustworthy and unethical.

He did not present an entirely unfeeling figure: He promised to give a voice to laid-off factory workers, “the forgotten men and women of our country.”

And he offered compassion for the parents of people killed by undocumented immigrants — and outrage on their behalf.

“These families have no special interests to represent them,” he said. “There are no demonstrators to protest on their behalf. My opponent will never meet with them, or share in their pain.”

“These wounded American families have been alone,” he added. “But they are alone no longer.”

He had enlisted his children to make him three-dimensional, a task they carried out with just a handful of personal memories: of the encouraging notes he scribbled across their report cards, and of playing at the foot of his desk with Legos or Erector Sets while their father worked in concrete and steel.

Of course, turning a polarizing candidate into a likable leader is not Mrs. Clinton’s talent, either. For much of the past two years, she has emerged as an awkward and reluctant storyteller of her life, more comfortable with 10-point plans than with providing fresh glimpses into her formative years or candid accounts of her professional struggles.

But Mrs. Clinton, whose convention next week will extensively mine her biography, has started to undertake the humbling repair work that many Republicans had hoped Mr. Trump would begin on Thursday.

She has admitted some mistakes, conceded that many Americans do not trust her, and acknowledged her role in the partisan warfare that has alienated many voters.

On Thursday night, Mr. Trump reveled in that warfare, made no concessions and admitted no mistakes.

His America, he said, would be “bigger, and better and stronger than ever before.”

Just like him.