Will Oprah Winfrey's endorsement sway the presidential election in Barack Obama's favor? Could Barbra Streisand and Steven Spielberg's support help Hillary Clinton snag the Democratic nomination?

Then again, will John McCain vanquish the Democrats with the backing of Republican celebrities Ted Nugent, Marie Osmond and Heidi Montag?

How much influence do celebrities really have on voters? Surely, the media attention and fan adoration that celebs daily command must translate into great political prowess.

Don't count on it.

Many experts agree that while Americans are all ears when it comes to celeb endorsements of cars and beers, we don't care which candidate they support. When it comes to voting, we'd rather keep our own counsel.

"A celebrity who makes a candidate endorsement is really trying to bigfoot a decision that individual voters strongly believe they need to do themselves," said Ross Baker, a political scientist at Rutgers University, in New Brunswick, whose study House and Senate will be published in its third edition next month.

"People will even resent" being told how to vote, Baker said.

Media expert Ellis Cashmore said we tend to be deeply suspicious of entertainers who dispense political - or for that matter, scientific, medical or religious - advice.

"There is always the prospect of what Australians call the tall poppy syndrome - when those celebs overextend themselves and get chopped down," said Cashmore, who teaches at Staffordshire University in England. "As we know . . . part of the fascination with celebs is being a first-hand observer of their demise."

Baker and Cashmore's assessments are borne out by the numbers.

According to a December poll from Sacred Heart University, 80.7 percent of Americans "pay no or very little attention to celebrities when they make political or public- policy statements." The survey included 800 people, with a 3.5 percent margin of error. (The result was down slightly from 81.9 percent in 2003, the last time the poll was taken.)

The poll also says that as many as 59 percent of respondents say celebs should stay out of public policy altogether.

"Fans who pay to watch celebrities in movies and TV or listen to their music consider themselves to be customers of a sort," said Jerry Lindsley, director of the Polling Institute at Sacred Heart.

"When they're told how to vote, their reaction is to say, 'That's not what I'm paying you for.' " Lindsley said it's not uncommon for people to feel offended. He did concede that fans are curious how their favorite stars vote, but only in the same way they're curious about what cars they drive, or what cuisine they prefer.

An unscientific survey of revelers and concession stand workers at the St. Marziale Italian Festival in South Philly on Sunday found much the same result.

Petko Dimitrov, 35, of Center City, said that when it comes to voting, "I rely on my own ideas and opinions."

Dimitrov said he was especially turned off by entertainers who pretend to have access to special knowledge or expertise about policy matters. "Just because someone is famous doesn't mean they have a wider or better perspective," he said.

Port Richmond resident Susan Johnston said when stars preach politics, "I just ignore them. . . . They're entitled to their opinions, but sometimes they push too hard, they're too aggressive."

So, then, if the public ignores them, why is it that more and more entertainers seem compelled to share their politics?

Cashmore, whose books include Celebrity Culture and The Black Culture Industry, said he didn't doubt that many entertainers sincerely wish to edify the public. But their engagement in politics primarily serves to enhance their image by giving them an air of "gravitas . . . integrity and credibility."

According to Cashmore, weighing in on politics has to do with accruing "cultural capital - that intangible quality that celebs can acquire when consumers sense there is more to them than what they see on the screen."

Tufts University political scientist Daniel W. Drezner said to maximize their cultural capital, celebs need to "do a cost-gain analysis" to make sure their involvement in particular causes will not alienate too many fans. He said the safest way is for celebs to eschew party politics and instead align themselves with charities and other "do-good" ventures.

Bono is a perfect example, avoiding taking sides in political battles and, instead, working hard to build consensus around various causes, including African debt relief, which earned him face time with world leaders, including President Bush.

Drezner, whose 2007 book, All Politics Is Global, analyzes how globalization affects international power relations, said there's no better way to reinvent oneself in Hollywood than through good works.

"Just look at Angelina Jolie. Ten years ago her image was about tattoos, rough sex, and wearing vials of Billy Bob Thornton's blood around her neck," Drezner said. "Today. Jolie has royalty status because of her work with UNICEF and other international charities."

Drezner said he has no problems with celebs who acquire a better image by doing good. But he worries that the growth of "the philanthropy-industrial complex" threatens to make the process nothing more than a cynical ploy for good PR.

If Drezner's account of do-goodism makes the whole process sound too self-serving and cynical, consider that there now exists an entire public relations machinery devoted entirely to marrying entertainers with specific political or charitable causes.

As public relations expert Ronn Torossian points out, there are "political outreach groups" and PR firms whose job is to cultivate a list of celebrity spokespeople and activists for corporations, nonprofits, and political parties.

Torossian, whose 5W Public Relations firm has represented Sean "Diddy" Combs, Pamela Anderson and Snoop Dogg, said he would always advise celebs to make endorsement deals with nonprofits or political causes.

"There's no reason political endorsements can't be handled any differently than commercial ones," he said.

So, does this mean that celebrities are using political endorsements as another form of self-promotion?

It wouldn't do them much good if the public isn't listening. Said Baker: "I think people really look at their vote as sacred."

Contact staff writer Tirdad Derakhshani at 215-817-2164 or tirdad@phillynews.com.