Oprah Winfrey throws her support behind Barack Obama

Talk show queen Oprah Winfrey has thrown her support at presidential candidate Barack Obama, as he kicked off the first of a three-state tour.

Billionaire Oprah, 53, urged more than 18,000 people present on Saturday in Des Moines, Iowa, to support the Democratic presidential hopeful, 46, because he is "the one."

"I am not here to tell you what to think," Winfrey proclaimed, adding that she is not trying to do for Senator Obama what her book club has done for authors. "I am here to ask you to think."

The hugely influential Oprah, who praised Barack Obama for his stance against the Iraq war, said she has "voted for as many Republicans as I have Democrats," insisting her backing is not purely partisan.

"I want you to think seriously about a man who knows who we are and he knows who we can be," she said.

Winfrey also described what she thinks Obama will bring to the presidency. "I believe that Barack Obama will bring statesmanship to the White House," she said. "I believe that he will lead with strength, conviction, honor and compassion."

After introducing Obama and his wife Michele, 43, an audience member yelled that Obama should pick Oprah as his running mate.

"You want Oprah as vice president?" he asked. "That would be a demotion."

Hawaii born Obama is the fifth African American Senator in U.S. history, and the only African American currently serving in the U.S. Senate.