He took the helm of government on Thursday morning to a standing ovation from the National Assembly, which elected him in a nearly unanimous vote. Mr. Castro embraced him, lifting the younger man’s arm in triumph.
Mr. Díaz-Canel’s slow and steady climb up the ranks of the bureaucracy has come through unflagging loyalty to the socialist cause — he “is not an upstart nor improvised,” Mr. Castro has said — but he largely stayed behind the scenes until recent years.
Now, as leader, Mr. Díaz-Canel is suddenly taking on a difficult balancing act. Most expect him to be a president of continuity, especially because he arrives in the shadow of Raúl Castro, who will remain the head of the armed forces and the Communist Party, arguably Cuba’s most powerful institutions.
But Mr. Díaz-Canel also has to figure out how to resuscitate the economy at time when President Trump is stepping back from engaging with Cuba. On top of that, Mr. Díaz-Canel must find a way to manage the frustrations of a Cuban population impatient with the pace of change on the island — without the heft of his predecessor’s revolutionary credentials.
Such credentials have been the bedrock of political power in Cuba ever since Fidel Castro seized control of the nation in 1959. In the ensuing years, the Castros ruled over Cuba with ironclad control, bolstered by a cadre of loyalists, nearly all of whom had fought alongside them in the revolution.
In the end, the most effective opposition to the Castro brothers was time.
Fidel Castro handed power to Raúl in 2006, then died 10 years later at the age of 90. Raúl then ushered in some of the most substantial reforms in decades, and is now orchestrating yet another one — the passing of the torch to a new generation.
After opening up the economy to private investment and entrepreneurialism, expanding travel in and out of the country and re-establishing ties with the great enemy, the United States, Raúl Castro has selected Mr. Díaz-Canel to fill his shoes.
Despite recent efforts to raise his profile, Mr. Díaz-Canel remains a somewhat unknown figure both domestically and abroad. In 2012, he led the Cuban delegation to the London Olympics and accompanied Raúl Castro to an international conference in Brazil.
Still, “he is someone who has very little exposure to U.S. political or cultural figures,” said Daniel P. Erikson, a former State Department official. “He is simply not a known figure in the U.S., and frankly he isn’t that well-known in the rest of Latin America, either.”
Ever since Mr. Díaz-Canel was named first vice president in 2013, Cubans and Cuba watchers alike have scrambled to find out more about the enigmatic heir apparent, combing through his track record as party leader in the provinces of Villa Clara and Holguín, and later as minister of higher education, for clues on how he will lead.
In each position, according to those who knew him at the time, Mr. Díaz-Canel has been a quiet but effective leader, often with a progressive bent. Many called him a good listener, while others described him as approachable, free of the rigidness and inaccessibility of typical party chiefs.
Through it all, he has also been a relentless defender of the revolution and the principles and politics it brought.
Stories of his Everyman qualities have spread widely in recent years: how he rode his bike to work instead of taking a government vehicle during gas shortages; how he defended the rights of a gay club in Santa Clara in the face of protests; how he patiently listened to academics grouse (sometimes about him) as minister of higher education.
More recently, he was a leading voice in the push for internet access in Cuba, arguing that the nation could not seal itself off from the outside world. Though his beliefs remain very much within the party line, those who know him say he does not adhere to the belief that Cuba can exempt itself from the modernization necessary to participate in the global economy.
But in Cuba, the continuum of political thinking is not black and white. Often, conventional definitions of progressives versus hard-liners do not apply. Leaders can be both, and Mr. Díaz-Canel is an example of that. While he is seen as open to the ideas of others, as a younger man he led a campaign to stifle students who read and discussed literature that was not approved by the Communist Party, according to those who knew him at the time.
Last year, a video was leaked of Mr. Díaz-Canel addressing a group of party officials. In it, he lambastes the United States, claiming that Cuba had no responsibility to meet its demands under the reconciliation brokered by President Barack Obama.
He then went on a diatribe against a website whose work he considered subversive. He told fellow officials that the government would shut it down — no matter whether people considered it censorship.
The video was seen as a way for Mr. Díaz-Canel to shore up his credentials with hard-line factions within the government, and yet a review of his career shows that he has not shied away from confronting activities deemed out of bounds by the government, either.
Mr. Díaz-Canel grew up in the central province of Villa Clara, about three hours from Havana, the son of a schoolteacher and a factory worker. He studied electrical engineering at the Central University of Las Villas, where he was active in political life.
While unknown abroad, from an early age he was viewed as a rising star within Cuba’s Communist Party.
As a young man, he joined the Union of Young Communists, the party’s youth league, where he stood out among his peers. He later worked as a bodyguard to Raúl Castro. According to a friend who knew him at the time, the assignment allowed him to show loyalty to the cause, and drew Mr. Díaz-Canel close to both Raúl and Fidel Castro.
He served three years in the army, another node of power in the country, after which he resumed his slow climb up the party ladder.
In his 20s, he was named the party’s liaison to Nicaragua, the only other Communist government in the region at the time, a posting viewed as important to the Cuban government.
Rodolfo Stusser, 72, recalled meeting Mr. Díaz-Canel in the late 1980s, while working as a doctor during Nicaragua’s civil war. Dr. Stusser felt the other doctors around him were lazy, not serious about their work. And just as he began liking his life in Nicaragua, he was being deployed elsewhere. He took his complaint to the Cuban Embassy, where he ran into a young Mr. Díaz-Canel, who offered him a ride.
Dr. Stusser unloaded, listing the various injustices he felt were being visited on him. It was almost therapeutic, he recalled. Mr. Díaz-Canel, an up-and-coming member in the party at the time, sat quietly and listened for the duration of the 40-minute drive, he recalled.
“He just heard me,” Dr. Stusser said. “He did not say anything at all. It helped me.”
Not long after, Dr. Stusser found his fortunes reversed in Nicaragua. He was allowed to stay. And an official who was giving him the runaround made time to see him.
Dr. Stusser, who defected in 2010 and now lives in South Florida, always suspected that the soft-spoken Communist Party official who listened but did not speak had quietly worked his connections in Havana and Managua to sort out his issues.
Juan Juan Almeida, 52, recalls hearing Mr. Díaz-Canel’s name come up years later in conversations with his father, who was a prominent member of the Cuban Communist Party at the time. He remembers his father coming home one night in 1993 after a meeting in which officials discussed future leaders of the country.
José Ramón Machado Ventura, a member of the Cuban old guard, proposed a slate of young leaders and Mr. Díaz-Canel’s name was among them.
“Raúl responded: He’s trustworthy, but too young,” Mr. Almeida remembers his father telling him after the meeting. “This was the first time I had ever heard the name Miguel Díaz-Canel.”
From then on, he said, Mr. Díaz-Canel’s name came up often. He moved from one prominent job to another — including provincial posts where he developed a reputation as an effective and loyal functionary.
As first secretary in Villa Clara Province, Mr. Díaz-Canel came to office during the so-called special period, when the generous aid flowing to Cuba from the Soviet Union was abruptly cut off after its collapse.
Back then, Mr. Díaz-Canel took his bicycle to work rather than ride in the air-conditioned car he was entitled to as a prominent leader. It was the sort of move people still talk about in Villa Clara and its capital, Santa Clara.
Mr. Almeida, who also defected to the United States, said he and Mr. Díaz-Canel had many mutual friends, in particular musicians and artists whom Mr. Díaz-Canel had taken the time to support in their careers. The new president also has a son who is a musician in Argentina, Mr. Almeida added.
“He mixes with the intellectual class, goes to concerts and is close to young people,” Mr. Almeida said. “All of the people I know who we have in common speak very well of him. They don’t speak of him in dictatorial fashion.”
Academics and others in Havana declined to be interviewed about Mr. Díaz-Canel, because the government did not give them permission.
In Santa Clara, Mr. Díaz-Canel is remembered for his Bermuda shorts at a time when party officials wore more formal attire, and for wearing his hair long.
His beliefs also skewed liberal, residents say. He lent his support to one of the country’s only gay clubs, El Mejunje. When it opened decades ago, the club was a point of contention. But Mr. Díaz-Canel, who took his children to the club when it hosted children’s activities, consistently backed the club in the face of controversy.
“He supported us anytime there was a complaint made against us,” said Ramón Silverio Gómez, the club’s director. “He was an ally. And one day when I saw him he said, ‘You can keep counting on my support and my understanding.’”
Yet some saw Mr. Díaz-Canel’s persona as crafted and less genuine than is often supposed. Sure, he rode his bike to and from work. But he was always trailed by his personal security in vehicles, others said.
“It was a bit of demagoguery,” said Guillermo Fariñas, a well-known dissident and Cuban psychologist who grew up with Mr. Díaz-Canel in Villa Clara. “In terms of the gasoline, he was on a bicycle, but there were cars with security going behind him. It was a bit a manipulation of the people.”
Mr. Fariñas recalled how one night, while he was hospitalized, the power went out. This was during the time of greatest shortages in Cuba, in the 1990s.
At about 3 o’clock in the morning, Mr. Díaz-Canel, who was first secretary in the province, went to the hospital and began going from room to room, checking on patients and apologizing for the blackout.
Even back then, Mr. Fariñas was a known dissident. He was in the hospital recovering from a hunger strike.
“When they were outside my room, I could hear the state security agents telling him, ‘No, don’t go to that room. That’s a counterrevolutionary’s room,’” he recalled. “Díaz-Canel was like, ‘What do you mean, don’t go to that room? Of course I’ll go to that room!’”
Mr. Díaz-Canel entered, shook Mr. Fariñas’ hand and said, “Let’s not talk about politics.”
The men chatted briefly before Mr. Díaz-Canel rushed off to see the next patient.
“My impression was that he was doing politics,” Mr. Fariñas said.
Mr. Fariñas also recalled how, after graduation, Mr. Díaz-Canel became a teacher and party functionary at his university, joining a nationwide campaign to fight “negative tendencies” in Cuba.
“They tried to convince people that if you were not a real communist, you had to be sanctioned,” Mr. Fariñas said of Mr. Díaz-Canel. “He was the head of that at the university.”
It was part of the duality of Mr. Díaz-Canel, he added. Mr. Díaz-Canel could be accessible, friendly and modern — mingling with locals, playing basketball with the youth and listening to rock music. But he could also be a staunch advocate of communism and the revolution, willing to silence critics.
“He was very active, very militant and very unconditional in his loyalty to the regime,” Mr. Fariñas said.