(CNN) -- "We had a dream. Now it's a reality."

For many, Sen. Barack Obama is an agent of change, but some critics say he could make race relations worse.

That's the slogan on a popular T-shirt linking Sen. Barack Obama's presidential run to the Rev. Martin Luther King's dream of racial equality. It's one of several T-shirts -- including "Barack is my homeboy"-- that reflect African-Americans' euphoria over Obama's White House bid.

But there are others who warn that an Obama presidency could hurt African-Americans. They say an Obama victory could cause white Americans to ignore entrenched racial divisions while claiming that America has reached the racial Promised Land.

Paul Street, author of the forthcoming book "Barack Obama and the Future of American Politics," says Obama risks becoming an Oval Office version of talk-show host Oprah Winfrey. She and former Secretary of State Colin Powell are African-American figures whose popularity allows some white Americans to congratulate themselves for not being racist, he says

"They're cited as proof that racism is no longer a significant barrier to black advancement and interracial equality," Street said.

"This isn't new. Go to the 19th century, and Southern aristocrats would point to a certain African-American landowner who was doing well to prove that whites are not racist."

Nick Shapiro, an Obama spokesman, says Obama believes that America has made tremendous progress in the past 50 years. iReport.com: Biggest challenges for black America

"However, the suggestion that somehow Senator Obama's campaign represents an easy shortcut is not realistic," Shapiro said in a statement. "Senator Obama believes that we still have a lot of work to do, and that's not just true for the issues facing blacks or Latinos, but for women and other communities struggling to secure the basic necessities in life like jobs, housing, health care and quality education."

Are we a post-racial society?

Any suggestion that an Obama presidential victory could set back race relations may seem odd or even inappropriate. His presidential campaign has been framed by many observers as a glowing example of America's move to a "post-racial" society.

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"Racial polarization used to be a dominating force in our politics, but we're now a different, and better, country," Paul Krugman, a New York Times columnist, wrote last month about Obama's political rise.

The reaction in the African-American community to Obama's success has also been celebrated with joy.

When Obama became the presumptive Democratic presidential nominee in June, many African-Americans cried because they said they never thought they would live to see such a day. Vendors soon started selling T-shirts of Obama's portrait pasted alongside King in Walgreens stores and at online stores.

Yet there are a few political commentators who warn African-Americans that an Obama victory could be twisted to suppress the push for racial equality. Most of these commentators are African-American, but they also include white, Latino and conservative pundits.

These commentators say that there is a subliminal appeal to Obama's presidential candidacy that has been ignored. Obama doesn't just represent change; he represents atonement for America's ugly racial past for others, they say.

Steve Sailer, a columnist for The American Conservative magazine, wrote last year that some whites who support Obama aren't driven primarily by a desire for change.

They want something else Obama offers them: "White Guilt Repellent," he wrote.

"So many whites want to be able to say, 'I'm not one of them, those bad whites. ... Hey, I voted for a black guy for president,' " Sailer wrote.

Sailer cited another reason why many whites want Obama as president:

"They hope that when a black finally moves into the White House, it will prove to African-Americans, once and for all, that white animus isn't the cause of their troubles. All blacks have to do is to act like President Obama - and their problems will be over."

Glen Ford, executive editor of the online journal blackagendareport.com, offered some white Americans a free solution to the race problem: "Millions of whites came to believe Obama could solve the 'race problem' by his mere presence, at no cost to their own notions of skin privilege," Ford wrote in an essay in January.

Other African-American commentators say the "post-racial" tag attached to Obama could be used to dismiss legitimate black grievances.

Andra Gillespie, an assistant professor at Emory University's political science department, says Obama's success doesn't mean America has become a post-racial society. She says it may signal the decline of individual racism but not another form of discrimination: systemic racism.

"It doesn't mean that there aren't prejudiced people anymore," she said.

Systemic racism is a form of racism that's entrenched in institutions. Some argue that it's the primary cause for intractable problems in the African-American community that range from substandard public schools to disproportionate rates of imprisonment, she says.

Electing a black president does not mean that America is ready to take on systemic racism, Gillespie says.

"A rising tide doesn't lift all boats," Gillespie said. "Just because [Obama] gets elected doesn't mean the lives of poor black people are automatically going to improve."

It could actually get worse for poor African-Americans, she says.

"People could say if Barack [Obama] can succeed and someone can't get off of the stoops in the hood, it's their fault, and it has nothing to do with systemic racism," Gillespie said.

D. Yobachi Boswell, a blogger for Black Perspective.net, wrote in January that the prospect of an Obama victory was making African-Americans politically passive.

He wrote that too many African-Americans were "doping ourselves up on the euphoric opium" of a black president while forgetting that "we need fundamental change, not just Negroes in high places."

Boswell says he's concerned that an Obama presidency would discourage African-Americans from keeping leaders accountable.

"We can't give [Obama] a pass because he's black," Boswell said. "We just can't have a black face in a high place. We have to have people fighting for policies that actually help us."

Obama has responded to such criticisms before. In his "A More Perfect Union" speech in March, he dismissed claims that his candidacy was fueled by the desire "to purchase racial reconciliation on the cheap."

He acknowledged that racial disparities in education and wealth continued to exist and were linked to the legacy of Jim Crow and slavery.

"I have never been so naive as to believe that we can get beyond our racial divisions in a single election cycle, or with a single candidacy, particularly a candidacy as imperfect as my own," Obama said during that speech.

A black backlash against Obama?

Despite what Obama has said, his presidency could provoke a black backlash because the expectations are so high, others say.

African-Americans who would expect a President Obama to be a vigorous advocate for their cause may be disappointed by Obama's approach to race if he becomes president, some say.

Author Street says Obama may be a symbol of bold racial change but he is personally cautious about race. A President Obama won't want to appear to favor blacks, because he might lose political support if he appears as the "angry black man" in the White House.

Street says Obama understands that risk and has run as a "race-neutral" candidate who talks about racial oppression as something largely confined to the past.

"Barack plays a very active role in damping down race consciousness," Street said. "Race neutrality is one of the great characteristics of his campaign."

African-Americans may also be disappointed by an Obama presidency because they may have forgotten what Obama is: a politician, says David Sirota, author of "The Uprising," a book that examines how populist movements in America shape public policy changes.

"He's like any politician. He's cautious," Sirota said. "He's a potential vehicle for change, and I think he is a good vehicle, but he is just a vehicle."

His presidency may represent fundamental change, but that doesn't mean he will initiate such sweeping changes if he's elected.

"Politicians, even the best-intentioned ones, are weather vanes," Sirota said. "If the wind isn't blowing in the right direction, they will perpetuate the status quo."

It will take more than a presidential candidate to change the status quo; it'll take a movement, Sirota says.

"My concern is that people will think that by simply electing Obama, change will come, whether it's on race or economic justice issues," he said.

"If people believe that, then real change will not happen."

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