The past 36 hours showcased two Joe Bidens: the veteran president rallying voters in a swing state, and an 81-year-old man struggling to string thoughts together in a debate.

Why it matters: The public split screen isn't new to many inside the White House, where top aides have meticulously stage-managed minutiae such as Biden's sleep schedule, his orthopedic shoes, his walks to Marine One and his climb aboard Air Force One to try to blunt concerns about his age.

• Internally, many aides have seen flashes of an absent-minded Biden, but typically brush them off as ordinary brain farts because they usually see him engaged, eight current and former Biden officials told Axios.

But Thursday's debate has shattered the White House's efforts to show Biden at his best: a president capable of serving until 2029, when he'd be 86.