Talk show host Oprah Winfrey has long been a role model for black women because of her rags-to-riches story, her status as a tastemaker and her message of self improvement.

Now she hopes that popularity will translate into votes for Democratic presidential candidate Barack Obama as he vies with New York Sen. Hillary Clinton for the support of a crucial constituency -- black voters.

"We don't have to just dream the dream anymore. We get to vote that dream into reality," Winfrey told a crowd of thousands in a huge football stadium in Columbia, South Carolina on  Sunday in a reference to American civil rights leader Martin Luther King's "I have a dream" speech.

"I believe that now is the time for somebody like Barack Obama," said Winfrey, clad in a yellow jacket and appearing on stage with Obama and his wife, Michelle.

Blacks are expected to make up around half the voters in the Democratic primary in South Carolina, which will be held on Jan. 26, three weeks after the opening round of voting begins in Iowa.

In the most-hyped campaign tour of the 2008 White House race, Winfrey and the Illinois senator held two rallies in Iowa on Saturday and were headed to New Hampshire after the South Carolina event.

Obama's supporters estimated the audience in South Carolina at 29,000, and the candidate said it was the biggest crowd of his campaign. After turning up hours in advance to clear security, fans of Winfrey and Obama swayed to hip hop and rock music as they waited.

When he took the stage, Obama called himself the "third-best speaker" after Winfrey and his wife.

He said he was "riled up" that some believe that as a black man, it would be hard for him to win the race. "I remember some folks saying, 'Oh no, a black man can't win," Obama said. "I remember that. When folks tell me I can't do something, that's when I like to do it."    

Winfrey praised Obama for what she described as his wisdom and concern for ordinary people.

Her fan base among women could help Obama as he seeks to challenge Clinton's lead. In South Carolina, Winfrey's appeal as an African-American could be an added plus to a candidate running to become the country's first black president.

Winfrey has catapulted books to the top of best-seller lists through her book club, and her shows featuring serious topics such as child abuse have drawn awards and imitators.

"When Oprah talks, people listen," said Kimberly Willis Green, 34, who traveled from just outside Atlanta, Georgia for the Winfrey and Obama rally.

"I believe in Oprah and I believe that she's not going to lead us down the wrong path," said Lisa Kelley, 40, an elementary school assistant teacher from Columbia who said she arrived at the rally undecided.

"I'm definitely leaning towards Obama," Kelley said.

Clinton has led Obama and former North Carolina Sen. John Edwards in South Carolina, but her lead over Obama has narrowed in recent weeks and the black vote is considered up for grabs. - Reuters