Post-racial is a term that I had never heard before 2008, but I am now frequently hearing applied to Barack Obama. It has a complicated meaning and one that will prove to be controversial in the long run. The premise of the term is that American black politicians from the civil rights generation usually acted as spokesmen for the black community and acted as representatives of an "interest group", that commonplace of 1960s politics, whereas Obama is seen as transcending this appeal to merely one group and being capable of uniting the entire nation behind him. He is hence "post-racial" because he has moved across the racial divide and hence transcended it in the process.

This has aroused decidedly mixed feelings among African-Americans. In one of his books, Obama wrote that "rightly or wrongly, white guilt has largely exhausted itself in America." This phrase was, as British commentators are wont to write, totemic; it invoked a catchphrase, a phrase of those who accuse black leaders like Jesse Jackson or Al Sharpton of playing on "white guilt" about past injustice to advance the cause of equality. In the speech on race that Obama made after he was forced to denounce Reverend Jeremiah Wright, he went out of his way to distance himself from this earlier generation, saying that "Reverend Wright and other African-Americans of his generation grew up" without economic opportunity or basic services and were "angry" as a result.

He had praise for this generation, saying "what's remarkable is not how many failed in the face of discrimination, but rather how many men and women overcame the odds". But he was saying he was not part of it, and he even said that welfare policy could have "worsened" the situation - a charge that conservatives have been making since well before Daniel Patrick Moynihan, although rarely with such force. Then Obama used a Father's Day speech to a black audience this year to say that blacks needed to take responsibility for their families and their own destiny rather than constantly invoking the past. As I am sure you heard, this resulted in Jesse Jackson expressing the opinion that he would like to castrate the presumptive nominee.

The rift between Obama and the older generation of black leaders is very real, and it is based largely on him saying things like this. But doubtless there is more. Although Jesse Jackson came closest to building a national, post-racial constituency, he still fell far short; indeed, it is inconceivable that any of the old generation of African-American leaders could have transcended the racial divide. Despite everything they did for their community, they defined themselves in opposition to the power structure and to Washington.

Obama's genius has been to enter it, but this has come at the price of being seen as compromising himself. Hence older black politicians such as Jackson have to live with an enormous ambivalence, tempering their joy that an African-American candidate can be en route to the Oval Office with the disappointment that he sounds so very different to the leaders of the civil rights generation. The idea of the post-racial politician is that he is the fruit of the struggle of this earlier generation - that his candidacy is only possible because of the sacrifice they made - but that he does not, and cannot, share their outlook. There is a mindset for war, and a mindset for peace; Obama, who believes in the system's ability to reform from the inside, chooses the latter. Jackson's denunciation of this choice will not be the last.

The problems that Obama the post-racial president might encounter are manifold. Firstly, he will have to govern with extreme sensitivity to the possible charge that he favours African-Americans in his policy. While the breakthrough success of an African-American presidency is obvious, there is a real chance it could sour race relations if it causes a feeling among the white majority that he favours minority interests. I do not suggest that this feeling would necessarily be justified, but it is easy to see how his opponents could inflame it. This problem essentially stems from the fact that while Obama may be post-racial, American society is not; and so his actions will be read through a prism that may be inappropriate.

The second possible drawback is that with President Obama in the White House, proponents of affirmative action and those who wish to fight discrimation against the black community will suddenly lose a lot of force. Obama has stated his opposition to extensive affirmative action and tried to turn the attention to the working class as a whole, noting that "most working- and middle-class white Americans don't feel that they have been particularly privileged by their race" and hence do not favour affirmative action. This undoubtedly true reading of the American public causes some black leaders to go into apoplexy, as they would denounce the opinion of the public as severely misguided; yet it is the essence of the post-racial offering.

By proving that an African-American can become president, Obama seems to invalidate the need for affirmative action - or at least confirm that it is sufficient at its current level. But this flies in the face of the demands by black leaders to extend it. It seems to some black elders that, like the Ancient Greeks knew, your worst nightmare can be to have your greatest wish granted; no serious observer would claim that the U.S. has dealt with the legacy of its racist past, yet a black president seems to be the highest symbol that it has. The risk seems even worse when he is "post-racial", which is another way of saying that he has embarked upon the process of cultural assimilation that other ethnic groups in America have followed and become part of the mainstream.

Obama stands - as he constantly says - as a great symbol of what one man can accomplish in America's political system. His achievement is indeed a testament to the earlier generation of leaders and everything they accomplished, and it could likewise not have come to pass that anyone but the most (at least superficially) brilliant African-American would become the first man in his position. Yet he walks a narrow precipice between his future and his past, risking the wrath of the white majority if he appears biased or the black minority if he is seen to betray his roots. Elation will soon die if he is seen as not worthy of the racial mantle placed upon him.

Politicians can survive evisceration by the African-American community, and it is the hallmark of the new generation of black politicians that they risk this by focusing on issues other than race. There are many signs that a younger generation of blacks are losing an interest in the older politics of confrontation, and trusting in the system to deliver. Obama will become the symbol of the system's pledge to provide this deliverance; if he succeeds, historians and contemporaries will praise his balancing act and rightly judge him, in this realm at least, a great president. If he fails, resentment and anger will grow. Rarely has so much rested on one so untested, and yet rarely has history not proved itself full of the most delicious surprises.