WASHINGTON — President Joe Biden’s conduct behind closed doors, in the Oval Office, on Air Force One and in meetings around the world is described in the same dual way by those who regularly see him in action.

He is often sharp and focused. But he also has moments, particularly later in the evening, when his thoughts seem jumbled and he trails off mid-sentence or seems confused. Sometimes he doesn’t grasp the finer points of policy details. He occasionally forgets people’s names, stares blankly and moves slowly around the room.