He was known around the University of Delaware campus as the teetotaling semi-jock with a sweater around his neck — the type who seemed more consumed with date nights than civil rights and expected a certain standard of decorum from his companions, once threatening to break off an evening with a woman who lit a cigarette in his borrowed convertible.

And when Mr. Biden and his friends at Syracuse University law school happened upon antiwar protesters storming the chancellor’s office — the kind of Vietnam-era demonstration that galvanized so much of their generation — his group stepped past with disdain. They were going for pizza…

There is a version of these years that Mr. Biden prefers to share publicly: how he was captivated by the civil rights movement, coming to understand the racial divide as a teenage lifeguard in a Black neighborhood of Wilmington, Del.; how he was brokenhearted by the murder of his heroes, Martin Luther King Jr. and the Kennedy brothers; how he was motivated chiefly by an altruistic call to service.

If much of this accounting is plainly true in the abstract, those who knew him say, it also elides some finer points of Mr. Biden’s arc: his boundless personal ambition, his canny relationship-building as a political novice and, quite often, his conspicuous psychic distance from the activist fervor of the times as he plotted a path to office.