Race is the most divisive issue in America.

Those who suggest that Sen. Barack Obama’s (D-Ill.) bid for the White House demonstrates that a post-racial era has arrived have a very strong argument. Unlike black candidates in the past, such as the Rev. Jesse Jackson and the Rev. Al Sharpton, Obama does not stress his racial origins either explicitly or implicitly. He has taken care to avoid doing so, and that is a big part of his appeal and his plausibility as a candidate.

But even if, in light of this, one can hope the nation is making progress toward the day when race is a non-issue, it cannot plausibly be argued that such a day has arrived — as the dispute about racial issues between Obama’s campaign and Sen. Hillary Rodham Clinton’s (D-N.Y.) campaign makes plain.

No reasonable person thinks either candidate harbors racist opinions. And yet Clinton’s reasonable comment that it took President Lyndon Johnson to turn Martin Luther King’s civil rights agenda into legal reality, combined with former President Bill Clinton’s comment that the distinction between his wife’s position on Iraq and Obama’s was a “fairy tale,” has touched off more than a week of debate about racial sensitivity in the Democratic presidential campaign.

That debate is roiling the Congressional Black Caucus (CBC), which is expected to tackle the Obama/Clinton dispute during a caucus meeting on Thursday.

Rep. Emanuel Cleaver (D-Mo.) suggested that efforts to divide African-Americans in the Democratic presidential campaign are akin to the strategy once used by the Ku Klux Klan.

This is dangerous territory for the CBC and for the two leading Democratic candidates running for the White House. The Clintons have long had a political affinity with black Americans, and Sen. Clinton has picked up more endorsements from black lawmakers than has Obama. But the advent of the first black candidate with a realistic chance of winning the presidency has the potential to change the political calculus.

At this highly charged moment, which some see as a turning point in the nation’s politics, there will be winners and losers. The South Carolina primary, in which a high proportion of voters will be black, is just around the corner, and neither of the two leading Democrats wants racial controversy to knock his or her chances in that crucial contest.

Equally, the CBC, a caucus built on racial identity, does not want racial debate to split it and make it less effective on Capitol Hill.

So when the caucus meets Thursday, its members will have much to discuss and some fundamental things to agree on.