Barack Obama's celebration of his Irish ancestry under the glare of the global media did much more than put the village of Moneygall on Co Offaly on the map.
It reminded the world that the first black president of the United States has a white ancestry, which can be traced back to Falmouth Kearney, the shoemaker's son who set sail from Ireland for America in 1850.
Given the historical nature of Mr Obama's presidency, and the unusualness of having an absent – and deceased – Kenyan father, it is perhaps unsurprising that the more pedestrian side of his family tree has been overlooked. There have after all been a dozen US presidents with Irish forefathers.
But what is more curious is how the part played in his life by his late mother, Stanley Ann Dunham, has been underrated if not almost erased from the standard Obama narrative.
The president himself shares some blame for this. During his 2008 campaign, Mr Obama would refer only fleetingly to her upbringing in Kansas. It was a useful way of making his exotic background more ordinary. Or he would discuss her struggle with medical insurance companies when she was dying of cancer in 1995 to reinforce his argument for health care reform.
His bestselling memoir, Dreams from My Father, dealt with his struggle for racial identity and the shadow cast by his absent parent, Barack Hussein Obama I. He wrote in more depth about his maternal grandparents, who raised him in Hawaii during his teens, than his mother. His brief descriptions of her life as an aid worker encouraged the impression that she was something of a flake.
A new book, A Singular Woman: the Untold Story of Barack Obama's Mother by Janny Scott, a New York Times reporter, convincingly makes the case that Dunham was however by far the dominant influence on his life.
"To describe Dunham as a white woman from Kansas is about as illuminating as describing her son as a politician who likes golf," Scott writes in the prologue. "Intentional or not, the label obscures an extraordinary story."
Physically, Obama inherited his Dunham's prominent chin, her smile, and the habit of tilting her head to one side. But her moral effect on him was profound, as he has admitted in one of his few statements about her.
She also imbued him with a sense of public service and what Mr Obama described to Scott as an element of "naive idealism". "It was a sense that beneath our surface differences we are all the same," he said, citing a common theme of his oratory.
So why did Obama relegate his mother in his narrative? A friend of Dunham's quoted in the book suggested that as a politician there was no choice because her story was so alien to most Americans, some of whom were already uncomfortable with Obama's strange name and Muslim forebears in Kenya.
Dunham indeed lived a life almost as remarkable as her son's would prove to be. She had two children by different men from very different cultures that she met at the University of Hawaii: Obama's Kenyan father and Lolo Soetoro, an Indonesian. She spent most of her working life in Indonesia, slogging for years for a PhD as an anthropologist and specialising as a development officer in microcredit before it became commonly known.
Janny Scott said: "If you are trying wanted to avoid the unwanted assumption that there is something exotic about your background, you don't emphasise you grew up in Indonesia. But I don't think he was hiding her – talking or writing about your mother is always a complicated business." The media and the publishing world were besides more concerned with his blackness.
To the author's surprise, the president did not duck the tricky subject of the years he spent apart from his mother, which many Americans would regard as a parenting failure or a sign of self-indulgence.
Mr Obama told Scott he didn't fault his free-spirited mother's choices. Unhappy people make bad parents, he said. But with the detachment and dispassion that is integral to his character, he recognised that in retrospect some of her decisions "could be hard on a kid".
Dunham uprooted him to Indonesia as a six-year-old, and sent him home for a few months to his grandparents at the age of ten. When, three years later, she returned to Indonesia with her husband to pursue her career, he opted to stay in Hawaii with his grandparents.
Though she confided to a friend it was her hardest ever decision, Dunham also said she wasn't worried about young Barry. She told plenty of people that her son was gifted enough to become president of the United States.