DES MOINES, Iowa (AP) -- Oprah Winfrey said worry about the direction of her country and a personal belief in Barack Obama's ability to lead it pushed her to make her first endorsement in a presidential campaign, support with incalculable value in a tight race for the Democratic nomination.
Winfrey said she felt nervous and "out of my pew" as she addressed a gathering hall packed shoulder-to-shoulder in the largest gathering of Iowans in the campaign this year. But she did not hide her political convictions, making an argument for change from the Bush administration other than another Clinton in the White House.
The talk show queen did not mention the current president or Obama rival Hillary Rodham Clinton by name, but was not subtle about her feelings for Clinton's argument that Obama doesn't have the experience to be president when she voted to authorize the war in Iraq.
"The amount of time you spend in Washington means nothing unless you are accountable for the judgment you made," Winfrey said. She said from the beginning Obama "stood with clarity and conviction against this war in Iraq."
"There are times that I even worry about what happens to our country," Winfrey said, standing on a small stage before a sea of people in the 100,000-square-foot hall. "That is why for the very first time in my life I feel compelled to stand up and speak out for the man who I believe has a new vision for America."
The campaign distributed 23,000 tickets for the Des Moines event and more than 10,000 for another later in Cedar Rapids. Thousands of people, many who don't normally participate in politics, came into his offices, volunteered and attended caucus trainings to score tickets.
The campaign said 18,500 people showed up in Des Moines. At least one person near the stage holding Winfrey, Obama and his wife passed out, and paramedics came in to help.
Clinton countered Oprah-mania by debuting two other women on the campaign trail -- her mother, Dorothy Rodham, and daughter, Chelsea. Neither had appeared publicly yet with the senator in her presidential bid.
The reluctant Chelsea Clinton's public emergence normally would have been big news, but it was a last-minute announcement that was overshadowed by hype surrounding the talk show queen.
"Senator Clinton is a big fan of Oprah's, and she thinks it is great for candidates to have surrogates campaign on their behalf," said Clinton spokesman Jay Carson. "Though on January 3, Iowans are going to come out to caucus and make their decisions based on the actual candidates' record of fighting for and delivering change."
Clinton pledged "change across the generations" as she courted voters with her 88-year-old mother and 27-year-old daughter. "We're getting close to the caucuses," the senator said. "I always think it's better to go to the caucuses with a buddy. Today, I've got some buddies with me."
The Democratic race in Iowa is tight, with Obama, Clinton and 2004 vice presidential nominee John Edwards in a dead heat. Winfrey said she doesn't know if her influence on the presidential campaign will have the same impact as driving up the popularity of books and products featured on her show.
"I understand the difference between the Book Club and a free refrigerator," she said. "I understand the difference between that and this critical moment in our nation's history.
"Over the years, I have voted for as many Republicans as I have Democrats," Winfrey said -- one line that didn't draw applause in the partisan crowd. "This isn't about partisanship for me. This is very, very personal. I'm here because of my personal conviction about Barack Obama and what I know he can do for America."
She said she is "tired of politics as usual," which is why she seldom invites politicians on her show to spread their rhetoric. Obama, she said, has an "ear for eloquence and a tongue dipped in the unvarnished truth."
Obama spoke after Winfrey, and acknowledged that he was under no illusions that the crowd was there to hear him. Indeed, some people left during his speech, although the majority stuck around to hear him.
"You want Oprah as vice president?" he asked the crowd that responded with enthusiastic cheers. "That would be a demotion, you understand that?"
The Obama campaign is particularly interested in winning over women, who have been leaning toward Clinton in the polls.
Terri Johnson of Urbandale, Iowa, lined up about two hours before the Des Moines event with three of her five children along. She said she had not been involved much in politics before, but was drawn to the rally by both Oprah and Obama.
"I would have voted for him without her, but it's nice to see Oprah," Johnson said, joking that she hoped Winfrey would have one of her famous giveaways. "I'd love to get a car."
Winfrey planned to continue her campaign swing Sunday to two other key primary election states -- New Hampshire and South Carolina.
