I saw Biden cry in Manchester, N.H., in October when holding an infant that he was told was named after Beau. I saw him near tears in West Mifflin, Pa., the weekend before the election, when he was joined onstage by the former Pittsburgh Steelers Franco Harris and Mel Blount — which reminded him of the footballs the team owner sent to young Beau and his brother, Hunter, in the hospital after they were injured in the 1972 car accident that killed Biden’s first wife and baby girl.

On his deathbed, Beau advised his father to run, but many friends — including President Obama — didn’t think he was up to it emotionally, and the vice president finally agreed. “For all that’s important to me in almost a sacred sense,” he told me mournfully, the decision was unavoidable. “The family was broken, and I was more broken than I thought I was.” How broken? “I don’t know what I’d do if I was in a debate and someone said, ‘You’re doing this because of your son,’ ” he told me one late November day in his West Wing office. “I might have walked over and kicked his ass.”

And yet minutes later, he was standing at his desk, fidgeting and replaying what might have been in 2016. The South Carolina primary would have given him a strong start, he said, citing his internal polls there. “Hard to believe, but I was more popular with blacks than Barack was.”

Biden clearly loathes the new president; he said during the campaign that if he and Trump were in high school, he’d “take him behind the gym” for the way he bragged about groping women. Trump reminded him of the bullies who teased him as a child on account of his stutter, calling him “B-B-Biden.” But the politician who has long believed all politics is personal wants to keep it impersonal with Trump. “The president and I have concluded that there’s no value in making that ad hominem argument,” he told me of Obama. “It gets you nowhere.”

Biden wasn’t shocked that Hillary Clinton lost. He had noticed before the election that Trump was connecting with the people he grew up with in Pennsylvania. This shaped his thoughts on how Democrats should respond. When the subject of Trump came up aboard Air Force Two, Biden referred to a well-worn story about how, as a freshman senator, he saw Jesse Helms, the archconservative North Carolina Republican, ripping into a piece of disabilities legislation. Biden was furious about it and began attacking Helms to Mike Mansfield, the Democratic Senate majority leader. Puffing on his pipe, Mansfield asked Biden if he knew that Helms and his wife had adopted a disabled 9-year-old boy no one else would take. “Question a man’s judgment, not his motives,” Mansfield instructed.