The book, “Original Sin,” describes how Mr. Biden’s aides quashed concerns about his age. But the anonymous accounts show that many Democrats are still afraid to discuss the issue publicly.

Biden reportedly failed to remember top aides’ names and once didn’t recognize George Clooney. Aides also worried he would need a wheelchair.

When then-President Joe Biden invited comparisons to Franklin D. Roosevelt during a meeting with historians, the possibility he might end up in a wheelchair while in office was surely not what he had in mind.