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.

Jake Tapper and Alex Thompson’s new book is an investigative account of loyalists and family members who shielded the diminished president from full public view.