CHICAGO (Reuters) - Celebrity political endorsements do not get much bigger than Oprah Winfrey's.
But political experts say it is doubtful the popular U.S. talk show host can sway votes to fellow-Chicagoan and first-term Illinois Sen. Barack Obama, the way she persuades viewers to turn books into instant best-sellers or adopt her self-help philosophy.
"People say that she won't be able to snap her fingers and have Iowans jump," said Dennis Goldford, a political scientist at Drake University in Des Moines, Iowa.
"She will help furnish him with an audience of people attracted to her, for him to make his own pitch," Goldford said. "I think she can sell his books a lot easier than she can sell his candidacy."
Winfrey's book club choices have catapulted such tomes as "Anna Karenina" and "The Road" to best-seller lists, and her shows featuring serious topics such as child abuse have earned numerous awards, and imitators.
The media spotlight is expected to shine this weekend on big crowds at four joint appearances by Winfrey and Obama. On Saturday they hit Des Moines and Cedar Rapids, Iowa, and on Sunday they hit two other early voting state, with stops in Columbia, South Carolina, and Manchester, New Hampshire.
Iowa holds the first contest of the party nominating process with its January 3 caucuses. Last weekend's Des Moines Register newspaper poll showed Obama edging ahead of New York Sen. Hillary Clinton in Iowa, with former North Carolina Sen. John Edwards trailing just behind.
The campaign bills Winfrey as Obama's "special guest," and those wanting to secure a seat at the free Iowa events were asked to volunteer or take a caucus training course.
Obama and Winfrey are both African-Americans and both make their homes in Chicago.
"The back story here is that Oprah knows Obama," Northwestern University political analyst Reuel Rogers said. "Both are from Chicago, and she's known him for a long time. As she put it, she can attest to 'the depths of his moral authority.' It's a very distinct personal relationship. It makes me wonder if she got to know the other candidates, maybe she'd feel that way about them.
Three-quarters of the 8.6 million viewers tuning in to Winfrey's show are women, and she reaches 46 million unique viewers each week. More than half are over 50 years old, and older people are more likely to vote.
Any voters put off by Winfrey and Obama both being black would be unlikely to vote for Obama anyway because of his race, Rogers added.
While neither Iowa nor New Hampshire has a sizable black population, South Carolina does, and Obama has been vying with Clinton to win support from blacks and from women -- both strong Winfrey constituencies.
Still, Winfrey's celebrity is just that, analysts said, with limited sway over voters, although she could rouse some nonvoters to get involved.
But a Pew Research poll found that 69 percent of respondents would not be influenced by Winfrey's endorsement of Obama. Of the 30 percent who would be influenced, half were more likely to back her choice and half were less likely.
"Voters typically look for their cues on whom to vote for from political elites and individuals from their own lives, workplaces, and schools," Rogers said.
Still, there were those who found the notion of celebrity endorsements noxious.
"It's particularly sad there are some people will let them tell them how to vote," Des Moines resident and teacher Lee Jolliffe said. "It started out I didn't like Obama. Oprah's endorsement is icing on the cake. Obama is to politics what (frequent Winfrey guest and psychologist) Dr. Phil (McGraw) is to counseling: slick and shallow."
Editing by Michael Conlon and Eric Walsh