I first heard this question from a biracial man not long after Barack Obama's game-changing win in Iowa. Pundits then were calling him the first black man with a serious shot at the presidency, but since his mother was white and his father was Kenyan, this fellow asked me, isn't he really biracial?

So why is the press calling him a black man?

The easy answer is that Obama self-identifies as black, often calling himself "a skinny black man with a funny name" and telling PBS host Charlie Rose "If I'm outside your building trying to catch a cab, they're not saying, 'Oh, there's a mixed race guy.'"

But the truth is, Obama is making things easier for a world which would be calling him a black man, regardless of his choice. As I wrote last year, racial identity in America winds up being this odd combination of your own choice and the way the world sees you.

Tiger Woods found this out the hard way, when he tried to develop a public identity for himself that embraced all elements of his heritage. But in calling himself "Cablinasian" in a nod to his father (black, Chinese and Native American) and mother, who is from Thailand, Woods angered some black people, who felt his choice showed contempt for black culture. And the press was so eager to herald the arrival of a successful black athlete in golf, they couldn't resit using that term on Woods, even when he resisted it.

Obama, being a gifted politician, likely knows how black people would have reacted had he tried something similar. In a cover story called "When Barry Beecame Barack," Newsweek explores the complex journey a young Obama took in building a personal identity that was comfortable to him -- one that could acknowledge his African roots and enable his dream to bring large-scale change in America.

Even as he sells himself to voters as a leader who knows many lives -- black and white, poor and priviledged -- Obama took the racial identity which the world would accept best. These days, with a black wife, residence on Chicago's historically black South Side and (until recently) membership in a militantly pro-black church, his cred as a black man stands strong.

So the real answer to why journalists call Barack Obama a black man is because America hasn't yet found an acceptable niche to slot those who bridge different races and cultures (even news organizations' recent trend of calling Obama African American -- a term the Associated Press once avoided in its own stylebook outside of quotes -- feels like a bit of a dodge).

Maybe that's the next barrier we have left to break.