Let’s imagine that Franklin D. Roosevelt had possessed the same gift for longevity as Jimmy Carter and lived until he was 100. He would have died in1982, in Ronald Reagan’s second year in office.

A year-long hostage crisis led to a presidency that would shape American politics for decades. But how much of what really happened is public?

Mr. Carter said his spiritual rebirth was an “evolutionary thing” rather than “a flash of light or a sudden vision of God speaking.”