In today’s political culture, people running for President may announce their candidacy on the steps of their home-town city hall or on “The View,” but the full introduction comes with their book. Some candidates’ memoirs tell stories of humble beginnings and of obstacles overcome; some describe searches for identity; some earnestly set out detailed policy agendas. Nearly all are relentlessly bland. In 2017, Joe Biden, a longtime senator from Delaware, Barack Obama’s Vice-President for eight years, and now a candidate for the Democratic Presidential nomination, published an unusually raw memoir about the death, two years earlier, of his forty-six-year-old son, Beau, describing how it had threatened to undo him but ultimately brought his family closer. Beau, his father writes, was “Joe Biden 2.0,” a war veteran, a prosecutor, and a promising politician who “had all the best of me, but with the bugs and flaws engineered out.”

In the early months of the 2020 race, Joe Biden holds a lead over his many Democratic Party rivals, but he is hardly invulnerable. He is seventy-six and sometimes shows it. He often stumbles when defending his five-decade public history. Some voters will not easily overlook his support for the Iraq War, his treatment of Anita Hill and loose management of the Clarence Thomas confirmation hearings, his handsy, close-talking behavior with women, or his descriptions of his “civil” working relationships with segregationist lawmakers. Even his admirers concede that he is prone to senatorial bloviation. What often seems to redeem him with voters, as a former senior White House aide put it recently, is “how he’s responded to tragedy and what he’s learned from it.”

Yet the family story that Biden tells in “Promise Me, Dad: A Year of Hope, Hardship, and Purpose” largely glosses over a central character in Biden’s life. Biden writes, “I was pretty sure Beau could run for President some day, and, with his brother’s help, he could win.” Hunter Biden, who is forty-nine, is described as a supportive son and sibling. In speeches, Biden rarely talks about Hunter. But news outlets on the right and mainstream media organizations, including the Times, have homed in on him, reprising old controversies over Hunter’s work for a bank, for a lobbying firm, and for a hedge fund, and scrutinizing his business dealings in China and Ukraine.

There is little question that Hunter’s proximity to power shaped the arc of his career, and that, as the former aide told me, “Hunter is super rich terrain.” But Donald J. Trump and some of his allies, in their eagerness to undermine Biden’s candidacy, and possibly to deflect attention from their own ethical lapses, have gone to extreme lengths, promoting, without evidence, the dubious narrative that Biden used the office of the Vice-President to advance and protect his son’s interests.

At the same time, the gossip pages have seized on Hunter’s tumultuous private life. He has struggled for decades with alcohol addiction and drug abuse; he went through an acrimonious divorce from his first wife, Kathleen Buhle Biden; and he had a subsequent relationship with Beau’s widow, Hallie. He was recently sued for child support by an Arkansas woman, Lunden Alexis Roberts, who claims that he is the father of her child. (Hunter has denied having sexual relations with Roberts.)

On May 17th, the day before Hunter planned to appear at one of his father’s rallies, at Eakins Oval, in Philadelphia, Breitbart News published a story based on a Prescott, Arizona, police report from 2016 that named Hunter as the suspect in a possible narcotics offense.

Onstage at the rally, Jill Biden introduced her husband. “The Biden family is ready,” she said. “We will do this as we always have—as a family.” Seated in white chairs to the side of the stage were Ashley Biden, Hunter’s half sister; Ashley’s husband, Howard Krein; Beau’s children, Natalie and Robert Hunter; Hunter’s three daughters, Maisy, Finnegan, and Naomi; and Naomi’s boyfriend, Peter. The last seat in the row, with a piece of paper on it that said “Reserved,” remained empty.

In one of my early conversations with Hunter, he told me about his sadness at having missed his father’s event. “Beau and I have been there since we were carried in baskets during his first campaign,” he said. “We went everywhere with him. At every single major event and every small event that had to do with his political career, I was there. I’ve never missed a rally for my dad. The notion that I’m not standing next to him in Philadelphia, next to the Rocky statue, it’s heartbreaking for me. It’s killing me and it’s killing him. Dad says, ‘Be here.’ Mom says, ‘Be here.’ But at what cost?”

Hunter speaks in the warm, circuitous style of his father. Through weeks of conversations, he became increasingly open about his setbacks, aware that many of the stories that he told me would otherwise emerge, likely in a distorted form, in Breitbart or on “Hannity.” He wanted to protect his father from a trickle of disclosures, and to share a personal narrative that he sees no reason to hide. “Look, everybody faces pain,” he said. “Everybody has trauma. There’s addiction in every family. I was in that darkness. I was in that tunnel—it’s a never-ending tunnel. You don’t get rid of it. You figure out how to deal with it.”

Hunter Biden was born in 1970, a year and a day after Beau and a year and nine months before their sister, Naomi. His father was twenty-seven, and won his first election, to the New Castle County Council, in November of that year. Two years later, in an immense leap of ambition, he decided to run for the U.S. Senate.

Biden pledged that, in order to avoid potential conflicts of interest, he would never own a stock or a bond. Whatever money he had, he spent on property. His father, Joseph Biden, Sr., managed a Chevrolet dealership in Wilmington, and Joe grew up in a house with his parents, his three siblings, his aunt Gertie, and two uncles. He tried to re-create this arrangement for his own family. He liked historic houses, and bought a center-hall Colonial, built in 1723, on a four-acre lot in the village of North Star, about thirty minutes west of Wilmington. “The large houses were a way for all of us, including aunts and uncles, to have something special,” Hunter said.

Joe Biden depended on his family to help staff his campaigns. His sister, Valerie, who taught at the Quaker day school Wilmington Friends, served as his campaign manager. His brother Jimmy oversaw fund-raising; Frankie, the youngest, helped organize volunteers. When the children were babies, Biden’s wife, Neilia, carried them to community meetings. In November, 1972, Joe Biden was elected to the Senate.

That December, while Biden was in Washington interviewing staff for his new office, Neilia took the children to Wilmington, to go Christmas-tree shopping. At an intersection, the family car collided with a truck. Neilia and Naomi were killed almost instantly. Beau sustained numerous broken bones, and Hunter suffered a severe head injury. Hunter has frequently said that his first memory is of waking up in a hospital bed next to Beau, who turned to him and said, “I love you, I love you, I love you.” On January 5, 1973, Biden was sworn in as a senator in his sons’ hospital room.

Valerie and Jimmy devoted themselves to the boys’ recovery while Biden took up his role in the Senate. In 1975, he sold the North Star property, and the family moved into a house in Wilmington that had once been owned by members of the du Pont family. Biden, on returning from Washington, often put on a hazmat suit and went into the basement to scrape asbestos off the pipes. He, Hunter, and Beau planted trees and painted the house. Hunter told me that his father would dangle him upside down from the third-floor windows so that he could reach the eaves with a brush. So many people came and went that Tommy Lewis, an old friend of Biden’s who became one of his Senate aides, nicknamed the house the Station. Hunter recalled, “No door was ever locked. The pool was everyone’s pool.” He and Beau were “communal property,” he said. “Everyone had a hand in raising us.” In 1977, Joe Biden married Jill Jacobs, a high-school teacher. (Hunter calls Jill “Mom” and refers to Neilia as “Mommy.”)