President Obama's one-day visit to Ireland was a masterly orchestration of three visuals - one imaginary, two very real.

Imaginary visual: the apostrophe in O'Bama. "My name is Barack Obama," he said in Dublin, "of the Moneygall Obamas, and I've come home to find the apostrophe we lost somewhere along the way." Anglo-Irish apostrophe, Kenyan last name, American tale.

Second visual, potent indeed: that imperial pint of Guinness at Ollie Hayes' pub in Obama's ancestral town of Moneygall (Irish Muine Gall, or "thicket of foreigners"!). Queen Elizabeth wouldn't touch Guinness when she visited, but Obama laid to with manly resolve - not as the U.S. construct "black man," but as an American toasting his Irish heritage.

Third visual, even more potent: the slim, assertive technocratic couple, politicians, parents, and partners: Michelle and Barack Obama, 21st-century bridges among Americas, Africa, and Europe.

Obama was doing much more than playing to the folks at home, with a wink to Moneygall. He was doing no less than seeking to reverse American notions of race, origin, and ethnicity.

"Clearly, a political bet is being made here that this will make beautiful political theater for 2012," says Matt Wray, assistant professor of sociology at Temple University. "But that isn't where the conversation ends. There's a performance here of race and ethnicity that does suggest the terms are changing in the U.S. These images of Obama quaffing Guinness as a son of Ireland really do strike even casual observers as historically new."

Consider the irony of a man so long under fire for his origins, comes to Ireland to celebrate one strand of those origins. He is called black because in the United States, we are messed up about origins. Why not call him "Barack Obama, America's 44th white president?" Or "America's third Irish American president" (after Ronald Reagan and John Kennedy)? He is as much those things as its first black president. No? Never happen? Why not?

Charles Gallagher, chairman of the Sociology, Social Work and Criminal Justice Department at La Salle University, sees the notorious "one-drop rule" of U.S. social attitudes at work: "A single 'drop of black blood' negates your ability to reconnect back to Europe. Race trumps all other questions of ethnic origin. Yet we know that 80 percent of all African Americans have European ancestors. Their history, which includes slavery, has cut them off both from Africa and from Europe, from being able to reclaim that great-grandfather in Sicily or Eastern Europe."

In his 1995 memoir Dreams From My Father, Obama told of his Kenyan ancestors. His visit to his father's Luo homeland is largely one of disappointment and sober reappraisal. At the time, New York Times reviewer Paul Watkins found "no emotional investigation into his other half, his 'white side.' . . ."

But, as Wray points out, Obama's much-praised May 18, 2008, speech on race, "A More Perfect Union," at the Constitution Center "spoke quite directly of the fact that he's the child of a white mother and black father and has white grandparents in Kansas. He has loyalty to two historically divided camps. That's what makes him such a powerful crossover figure."

Obama's speech in Dublin told of Fulmouth Kearney, his grandfather's grandfather, who got out of tiny Moneygall in 1850, ended up in Ohio, bought land, and started a line of middling, obscure, working Americans. How was Kearney to know his line would braid with a Kenyan line, to run within an American (yes) president? An American tale.

Gallagher says, "What Obama did is fantastic. He's telling the truth: that ethnicity is absolutely fluid, and you can reclaim the full spectrum of your identity. It's further blurring of the color line, and it gives permission to Americans, many of whom have incredibly diverse origins, to explore them all."

As Wray puts it: "It speaks to the fastest-growing segment of Americans - those of mixed race - starting to rewrite the script. Obama, in his blackness, is free to explore his whiteness."

The circle won't be closed, of course, until millions of white Americans embrace the Africa in their pasts. Forty million claim Irish roots. How many will claim African?

The Anglo-Irish apostrophe, as in O'Reilly or O'Bama, derives from the Irish Ó, a sign of belonging. In his every Irish step, Barack Obama asserted a new picture of belonging - for himself and all who want to rebuild bridges to their multiple pasts.