DENVER (AP) — Barack Obama achieved a historic breakthrough with his nomination for president, but you wouldn't know it by tracking the official events of the Democratic convention's first three days. In becoming the first black American to claim a major party's nomination, Obama has reached a milestone that many felt was at least a generation away. But the convention, like Obama's overall campaign, thus far has dealt with race lightly, obliquely, or often not at all.

Prominent black lawmakers addressed the Denver crowd Wednesday without mentioning the campaign's racial dimensions, which they eagerly and emotionally discuss in private. Americans watching TV might assume otherwise because convention commentators often discuss race. But they are drawing from interviews and other sources, not from the speeches that are vetted by the Obama campaign and that serve as a record of the four-day event.

Obama is "running as a candidate who happens to be African-American, not as an African-American who happens to be running for president," said Chris Lehane, a spokesman for Al Gore's 2000 presidential campaign. The reason is simple, campaign strategists say. The more Obama is seen as a black candidate, the greater the risk that some white voters might reject him. In Denver, the omissions are notable because several convention events have celebrated Hillary Rodham Clinton's unprecedented achievements as a female presidential candidate.

The tone changed yesterday, as Obama prepared to accept the nomination on the 45th anniversary of Martin Luther King's "I Have a Dream" speech, a coincidence that could hardly be ignored. But when Obama resumes campaigning today in Pennsylvania, party insiders expect him to revert to his practice of soft-pedalling race: acknowledging its role in American society, when asked, but rarely bringing it up on his own, and never using it as basis for seeking people's votes.

"No one is going to forget that Barack Obama is half black," Pennsylvania Gov. Ed Rendell said Wednesday. But in seeking his state's crucial white, working-class voters, Rendell said: "I wouldn't emphasise it. I'd say, 'Look, right now I think the only colour you're concerned about is green'," a reference to families' economic worries.

Obama, the son of a black father from Kenya and a white mother from Kansas, often says that race's role in American society is undeniable, but he does not want people to vote for or against him mainly because of his race. In his presidential campaign, he has addressed race in a lengthy, comprehensive way only once: on March 18, when incendiary remarks by his former pastor threatened his campaign. "Race is an issue that I believe this nation cannot afford to ignore right now," Obama said in Philadelphia. He later broke all ties with the minister, the Rev. Jeremiah Wright, and has not addressed race again in anywhere near the depth he did that day.

In Denver, the party has passed up obvious opportunities to celebrate Obama's achievement in a nation whose legacies of slavery and segregation still feel fresh to many. On Wednesday, three of the House's most senior black members — Maxine Waters of California, Elijah Cummings of Maryland and Democratic Whip Jim Clyburn of South Carolina — addressed the convention without alluding to race.

In Denver's hotels and restaurants, of course, talk of racial politics is more commonplace. Some of the bluntest speakers are white labour union leaders, eager to help Obama win working-class votes in key states such as Michigan, Pennsylvania and Ohio. "There are a lot of white workers, and frankly, some of them are union members," who refuse to vote for Obama "because they think he's the wrong race," Richard Trumka, the treasurer of union federation AFL-CIO, told Ohio delegates this week. "We cannot tap dance around the fact."

"Race is a tool that is used to divide working people," Trumka said. He called on Democratic activists to convince blue-collar workers that Republican John McCain's policies would harm their interests. If black delegates say little about race on the convention stage, many are privately exulting over Obama's nomination. "This reflects what Dr. King was talking about" in the 1963 "dream" speech, said James W. Crowell, treasurer of the Mississippi chapter of the National Association for the Advancement of Colored People.

Martin Luther King III said that his father's dream is not totally fulfilled but that Obama is wise to keep from making race central to his candidacy. The campaign, he said, "shouldn't be about black issues or white issues. It should be about issues for every American."

Rendell, the Pennsylvania governor, said families struggling to pay their bills are more likely to vote on pocketbook issues than on matters such as race, which should help Obama.

People will choose their candidate, he said, based on "who's most likely to help them with their financial condition. If the answer is Barack Obama, nobody's going to care whether he's black, green, orange, purple, fuchsia or whatever."