ROME — In 1965, John F. Kerry and David Thorne were college-age kids driving around Europe together in a used English cab they bought for $100 and named Baxter. Inspired by Ernest Hemingway, they went running with the bulls in Pamplona. They drove around England, through France, along the Italian coast, two young men with a summer to kill.

The friendship has shaped Kerry’s life in so many ways that even Hemingway might have found it too far-fetched for a plot line. The two were side by side in Yale’s secretive Skull and Bones society. They went off to Vietnam and returned to lead antiwar protests together. Kerry married Thorne’s twin sister. Thorne was by Kerry’s side when he lost his presidential bid.