That an air of the enigmatic attends Barack Obama is a commonplace; he is a man of fractured geography and family and wanderings.

He came of age in far corners, Indonesia and Hawaii, went to schools on both coasts and landed in Chicago, where he had no blood tie. With talent and ambition, he has leapt for the presidency at a tender age and will go to Denver to claim his Democratic nomination for the office.

There is to Mr. Obama’s story a Steinbeck quality, like so many migratory American tales: the mother who flickers in and out; the absent and iconic father; the grandfather, raised in the roughneck Kansas oil town of El Dorado, who moves the family restlessly, ceaselessly westward.

The American DNA encodes wanderlust ambition, and a romance clings to Mr. Obama’s story. The roamer who would make himself and his land anew is a familiar archetype....

Mr. Obama offers a duality in this regard. He might be seen as chasing after roots. As a young man, he sought out precinct captains and ministers and tenants, and convinced the suspicious locals to teach him the ways of Chicago. He is married and never divorced, two children, a resident of the Midwestern city for two decades. “Obama is the least mobile candidate in the race,” says Alan Wolfe, a professor at Boston College. “He’s almost single-minded about that.” There is, too, the sneaking suspicion that describing Mr. Obama, multiracial and multiethnic, as rootless could become a surrogate for something darker. In American history, whites accused Indians of rootlessness before dispossessing them. Jews and Italians, Socialists and anarchists: all stood accused of being “the other.” “My sense, for what it’s worth, is that the charge of ‘rootlessness’ is suspect, and has an ugly genealogy,” Mr. Delbanco said.