A historically diverse field of Democratic presidential candidates — a woman, a black, an Hispanic and five whites — denounced an hours-old Supreme Court affirmative action ruling Thursday night and said the nation's slow march to racial unity is far from over.

"We have made enormous progress, but the progress we have made is not good enough," said Sen. Barack Obama, the son of a man from Kenya and a woman from Kansas.

Sen. Hillary Rodham Clinton, the first female candidate with a serious shot at the presidency, drew the night's largest cheer when she suggested there was a hint of racism in the way AIDS is addressed in this country.

"Let me just put this in perspective: If HIV-AIDS were the leading cause of death of white women between the ages of 25 and 34 there would be an outraged, outcry in this country," said the New York senator.

In their third primary debate, the two leading candidates and their fellow Democrats played to the emotions of a predominantly black audience, fighting for a voting bloc that is crucial in the party's nomination process.

One issue not raised by questioners, the war in Iraq, dominated the past two debates. Queries about AIDS, criminal justice, education, taxes, outsourcing jobs, poverty and the Bush administration's response to Hurricane Katrina all led to the same point: The racial divide still exists.

"There is so much left to be done," Clinton said, "and for anyone to assert that race is not a problem in America is to deny the reality in front of our very eyes."

While the first two debates focused on their narrow differences on Iraq, moderator Tavis Smiley promised to steer the candidates to other issues that matter to black America. In turn, the candidates said those issues mattered to them.

"This issue of poverty in America is the cause of my life," said John Edwards, the 2004 vice presidential nominee.

Said Obama: "It starts from birth."

Obama criticized President Bush's No Child Left Behind program. "You can't leave money behind ... and unfortunately that's what's been done," he said.

Clinton spoke of her efforts in Arkansas to raise school standards, "most especially for minority children."

Delaware Sen. Joe Biden urged people to be tested for the AIDS virus, noting that he and Obama had done so. Cracked the Illinois senator: "I just want to make clear I got tested with Michelle," his wife, Obama said drawing laughter from the predominantly black audience.

The debate was held at Howard University, a historically black college in the nation's capital.

Black voters are a large and critical part of the Democratic primary electorate, making the debate a must-attend for candidates seeking the party's presidential nomination.

A half century of desegregation law — and racial tension — was laid bare for the Democrats hours before they met. In a 5-4 decision, the Supreme Court clamped historic new limits on school desegregation plans.

Clinton said the decision "turned the clock back" on history, and her competitors agreed.

The conservative majority cited the landmark Brown v. Board of Education case to bolster its precedent-shattering decision, an act termed a "cruel irony" by Justice John Paul Stevens in his dissent. The 1954 ruling led to the end of state-sponsored school segregation in the United States.

Obama, the only black candidate in the eight-person field, spoke of civil rights leaders who fought for Brown v. Board of Education and other precedents curbed by the high court. "If it were not for them," he said, "I would not be standing here."

Biden noted that he voted against confirmation of Chief Justice John Roberts, who wrote the majority opinion. He said he was tough on Roberts. "The problem is the rest of us were not tough enough," he said, seeming to take a jab at fellow Democrats. "They have turned the court upside down."

All the Democratic candidates in the Senate opposed the confirmation of conservative Justice Samuel Alito, another of President Bush's nominees. Clinton, Biden and Obama voted against Roberts; Sen. Chris Dodd voted for his nomination.

New Mexico Gov. Bill Richardson, the first major Hispanic candidate, said race is about more than passing new laws and appointing new justices. "The next president is going to have to lead," he said, vowing to do so.

Dodd said "the shame of resegregation in our country has been occurring for years."

The nomination fight begins in Iowa and New Hampshire, two states with relatively few minorities. But blacks and other minority voters become critical in Nevada, South Carolina and Florida before the campaign turns to a multi-state primary on Feb. 5.

About one in 10 voters in the 2004 election were black, according to exit polls, and they voted 9-to-1 for Democrat John Kerry. In some states, blacks make up a bigger share of the voters. In South Carolina, for example, blacks made up about 30 percent of the electorate in 2004, but were more than half of the voters in the state's Democratic primary.

Massachusetts Gov. Deval Patrick, the country's only black governor, introduced the candidates with a warning that a dispirited GOP "is not enough to elect a Democratic president nor should it be. We need to offer a more positive and hopeful vision ... to run on what we are for and not just what we are against."

Ohio Rep. Dennis Kucinich and former Alaska Sen. Mike Gravel also debated.