Sometimes a candid photograph captures a moment in a presidency, and the essence of the officeholder, so tellingly that you get a penetrating portrait of an era.
It happened when L.B.J. yanked up his beagle by the ears for photographers and demonstrated his domineering leadership style.
It happened when a photographer captured W. being told, while reading to children in a Florida classroom, that a second plane had hit the World Trade Center. His look of shock raised questions about whether, after his decades of winging it, a parlous rendezvous with destiny might be too much for him to handle.
