Conventions tell us a lot about America's political parties but so does what happens elsewhere in election year. One such "elsewhere" event is the race to represent Illinois in the US Senate. The candidates in this instance are both black. The Republican is Alan Keyes, who ran for president in 1996 and 2000. The Democrat is Barack Obama, the star at his party's national convention last month. Both Mr Keyes and Mr Obama are innovators who seek to topple old political assumptions about race.

Illinois has a record as host to such innovation. It was in pre-civil war Illinois towns such as Charleston and Galesburg that an ambivalent Abraham Lincoln, the Republican candidate for the US Senate, tried out the relatively novel idea that the black man "was as much entitled" to constitutional rights as the white man. Lincoln lost, but his debates with Stephen Douglas set the stage for the war and emancipation. The result of these changes was a strong Republican party, supported by black people for multiple decades.

After the Great Depression, and especially with the rise of the civil rights movement, Illinois again played a role. Elijah Muhammad built up the radical Nation of Islam movement on Chicago's South Side. Jesse Jackson, the civil rights activist, also picked the South Side as headquarters. In the early 1970s Mr Jackson established Push (People United to Save Humanity), an institution operating on the then-bold theory that black people could only advance if they made themselves felt as a distinct force. Most black people were already Democrats by the time he arrived. Mr Jackson tied black activism to the party; Obama-like, he lit up conventions and ran repeatedly for president.

The change helped black groups win political battles. But it also hurt the black cause generally by creating a standard party-linked interest group, not much different from, say, organised labour or AARP, the senior citizen lobby. The Jacksonesque emphasis on race also put off old liberals and centrists, even when they did not say so. Martin Luther King, after all, had not asked that his children be guaranteed slots at certain universities or government contracts for construction; he asked that they "be judged not by the colour of their skin but by the content of their character". Unwilling confirmation of the problems of emphasising race was provided by Carol Moseley Braun, an Illinoisan who became the nation's first black woman senator. Ms Braun is a likeable person who performed her Senate job as though she were representing black people, not Chicagoland or Springfield. This - as much as the odd scandal - prevented her re-election.

Such attitudes gave Republicans an opening: the chance to remind everyone that they were the party of Lincoln, the higher, the colourblind. President George W. Bush did this by leaning on Condoleezza Rice and Colin Powell in his first campaign and by giving the pair the nation's most important foreign policy jobs. But there were other Republicans who also pushed a post-racial agenda. One was Mr Keyes, a Harvard-trained radio debater and an evangelist. Rather than focus on race in his run for president four years ago, Mr Keyes fought against abortion and for states' rights. These positions were unusual. The cliché is that all black people are pro-democrat and all democrats pro-choice. States' rights? They are the traditional defence of segregationists. Still, Mr Keyes defended his points well, at least as well as Mr Jackson and perhaps as well as Honest Abe. Republican voters in Iowa rewarded him with one in seven votes.

In a hypothetical contest against Carol Moseley Braun, Mr Keyes might have had a shot at a new-beats-old victory. Against Mr Obama, his chances are slim. For Mr Obama also comes out of a meritocratic culture - he led Harvard's law review, a privilege reserved for top students. As a state senator in Illinois he has focused much of his work on economics or education, not race per se.. In Boston, Mr Obama said: "There's not a black America and white America and Latino America and Asian America; there's the United States of America."

This is not different from what Mr Keyes has long been saying. In 1996 he told Texan Republicans: "We do not believe that this can be a house divided" (the phrase itself an echo of Lincoln's Springfield "House Divided" address). What is new about the Obama message is that it is coming from a Democrat. The Obama speech was the party warning shot: we too, it says, have a post-quota, post- interest-group culture. The adoration in which Mr Obama has bathed since July suggests voters like the news.

In other words, the contest tells us two things. The first is that Illinois is yet again emerging as the venue for a shift on race. Mr Obama and Mr Keyes will debate, and their debates will be a new thing for post-civil rights America, one in which two black people both argue that skin colour matters less than opportunity. The prospect of this exchange - and not that of victory - is what draws Mr Keyes to Illinois. But the Keyes-Obama contest, whatever its outcome, could be good for the Democratic party nationally. By recapturing the American centre on the race question, the party may tip the balance of power generally in its own favour in a way that will matter past November. Right now most of us observers are preparing for the Republican Convention in New York. Still, the big show of 2004 may well take place in the Land of Lincoln.

© Copyright 2004 Financial Times