09/28/2012 03:00 pm ET

‘Bill And Hillary' By William H. Chafe

How far can a presidential marriage go in explaining a presidency?
Not far, according to most couples who occupy the White House. Life and history are smoother for them if everyone abides by the press-office fiction that the president’s spouse is more soothing accessory than sharp-eyed adviser or moral force. So while we stare endlessly at first couples, we rarely glimpse the strange vastness of their marriages: how a private conversation between two people, ­lying in the same bedroom where Abraham Lincoln slept, can influence an entire nation.