Students of history may recognize a concept I’ll call the Weirdo Theory of Crisis. In times of upheaval and strife (so goes the theory), unconventional figures have a way of slipping into power. They were also, in various combinations and to different degrees, messy, wounded human beings. “During prosperous times, none of Roosevelt’s up-and-coming lieutenants could have ventured far beyond political suburbia,” as Mr. Lebaert puts it. “Then the Great Depression changed everything.” Weirder still, these four survived into Roosevelt’s unprecedented fourth term, outlasting nearly every other secretary or top adviser, aside from the First Lady.

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