Maybe it was Michelle's repeatedly insisting Barack was raised by a single mother but they cleaned up Barack's bio (and Ann's) with very little attention from the media.
From "Meet The Candidate" at the Obama - Biden website:
Early Years
Barack Obama was born in Hawaii on August 4th, 1961. His father, Barack Obama Sr., was born and raised in a small village in Kenya, where he grew up herding goats with his own father, who was a domestic servant to the British.
Barack's mother, Ann Dunham, grew up in small-town Kansas. Her father worked on oil rigs during the Depression, and then signed up for World War II after Pearl Harbor, where he marched across Europe in Patton's army. Her mother went to work on a bomber assembly line, and after the war, they studied on the G.I. Bill, bought a house through the Federal Housing Program, and moved west to Hawaii.
It was there, at the University of Hawaii, where Barack's parents met. His mother was a student there, and his father had won a scholarship that allowed him to leave Kenya and pursue his dreams in America.
Barack's father eventually returned to Kenya, and Barack grew up with his mother in Hawaii, and for a few years in Indonesia. Later, he moved to New York, where he graduated from Columbia University in 1983.
Gone is any mention (claim?) that Barack Sr. and Ann were married (or divorced). Also vanished is Barack's step-father -- in his life much longer than his father. Interestingly, he now appears to have never lived with and been raised by his maternal grandmother.
Remember America, history is what Barack says it is. Stay up on the latest revisions. We'll be shooting the pink pages later today. Memorize them!