In 2004 John Edwards went around the country proclaiming the existence of two Americas. One reason his candidacy did not go further than it did was that his appeal often fell on the ears of people tired of divisiveness. After a generation of polarized politics Americans were eager for national unity--or at least a call for unity. Sensing this need, Barack Obama, in the speech that launched his national career, declaimed at the 2004 Democratic Convention: "there is not a black America and a white America.... There’s the United States of America." This sounded fresh at the time, but it was actually an old refrain in American history of an idea born in the years when the country became a haven for millions of immigrants from around the world.

In its original incarnation the appeal to national unity was a deliberate slap in the face of immigrants. Fed-up with the changes immigrants were bringing to America, mainstream white Protestants who traced their ancestry to the Mayflower began in the late nineteenth century to long for the kind of national unity they vaguely remembered from their youth before Italians, Slavs, Jews, the Irish and others emigrated to the United States in large numbers. Politicians like Theodore Roosevelt, eagerly responding to this feeling, inveighed against so-called hyphenated Americans. "Be Americans, pure and simple," Roosevelt proclaimed.

More than rank bigotry lay behind the concern with "hyphenates," as they were derisively labeled. U.S. foreign policy was constantly being tugged this way and that by immigrant groups eager to use their power at the ballot box in America to settle scores left-over from the Old Country. Irish-Americans, with the memories of British tyranny over Ireland still fresh, demanded that the United States twist the Lion's tail. German-Americans on the eve of World War I sided with the Kaiser over the Allies. In the event of actual war immigrants usually rallied around the flag with the same fervor as other Americans, but their true loyalty seemed in doubt to many. Roosevelt complained, "When two flags are hoisted on the same pole, one is always hoisted undermost. The hyphenated American always hoists the American flag undermost."

Though largely forgotten today, for decades American politics was roiled over concerns about white European immigrants. Even highly educated Americans could fall for anti-immigrant appeals. The highly esteemed historian Thomas Bailey, writing in 1948, shockingly let loose this screech: "when the melting pot bubbles, often with European faggots under its bottom, the scum rises to the top." Bailey, himself the child of immigrants, was no bigot. But he felt keenly that our politics were too often shaped by demagogic responses to individual groups making self-serving demands.

While Americans remain divided over immigration politics, as anyone who watches Lou Dobbs on CNN is aware, the chief issue separating Americans recently has been the so-called culture war, which Democrats and Republicans have each exploited for a generation. (We have moved from"boiling pots" to" culture wars." Progress?) Underlying many of the points of conflict in our culture war have been questions involving race.

Like Theodore Roosevelt, Obama is responding to events. Unlike Roosevelt, however, Obama's call for national unity is clearly not motivated by a desire to squelch the feelings of a minority in the name of some larger good. As he made clear in recent days his intention is to get people talking about their differences openly and honestly. Where Roosevelt wanted to silence Americans who held strong feelings with which he felt uncomfortable, Obama, drawing on a Sixties-era sentiment, wants people to express themselves.

Whether national unity is possible under the circumstances is doubtful. The more we talk the more we may discover that we are different. One of the most remarked about topics of the last few days have been the surprisingly sharp differences in opinions between blacks and whites over a variety of subjects. The New York Times informs us that even Wright's claim that the United States government was responsible for the AIDS crisis was considered so uncontroversial in his black community (and others) that few thought it strange when he made the charge, even though it's groundless.

The irony of Obama's campaign may be that despite his intentions he may have done more to divide the country than any other living politician--at least in the short term. Looking back a generation from now this election might be a turning point in race relations if Obama's premise is correct that the more we talk the better off we'll be. But in the moment Obama's brave speech has opened a Pandora's box of fears and resentments that almost certainly will in the heat of a campaign prove difficult to deal with rationally.

Given that we lack a common ancestry it is natural that we are sensitive to signs of disunity. But how much unity can we honestly expect in a country as diverse as ours?

Our unity as a people has always been something of a myth. Obama played on that myth and in some sense gambled his candidacy on it. But it is one thing to believe in a myth and another to confuse it with reality. While we may all hope fervently that our country is unified, the grim truth may be that it is not and that we simply have to accept that.