AT A Center City dinner party, an intelligent, educated woman insists that Barack Obama is a Muslim. My husband's tennis buddy thinks Obama is "a Muslim plant," a Manchurian candidate sent to secretly take over the country.

Someone else believes that if elected, Obama plans to blow himself up in the White House.

"Give Obama a ham sandwich and see what happens" is a comment posted online under the moniker "Ataxicabdriver."

Michelle Obama described her husband as a loving parent reading Harry Potter to his daughters at bedtime - and on a YouTube video, a man asks ominously, "Does Barack Obama oppose Harry Potter like most Christian parents?" or does he favor "witchcraft"?

Despite all the attention given to Obama's ex-minister and other doings at the United Church of Christ, a significant number of people believe that Obama is a Muslim.

Obama has repeatedly stated that he's a Christian and has never been a practicing Muslim. For some people, this only fuels fears that he is secretly a Muslim.

Where is this coming from? A conservative Web site, insightmag.com, published a story claiming that Obama was educated in a Wahhabi madrassa, a school teaching radical Islam and training terrorists. This false information was promptly repeated by Fox News without further investigation and disseminated to millions of people.

CNN sent a reporter to the school in Jakarta, Indonesia, that Obama attended at age 6. It is - and was when Obama went there - a public school with children of different religious backgrounds, male and female teachers, and boys and girls who mix freely on the playground - obviously not the stuff of radical Islam.

But the Web site's story took hold and spread quickly.

And so the doubts persist.

It's not hard to see why.

He has a name that's strange to many Americans: Barack Obama - doesn't that rhyme with Osama?

He doesn't use his middle name, Hussein, but it's been trumpeted by conservative media, implying some connection to Saddam Hussein, the dictator that America went to war to overthrow. Linking the names has been successful. "I've had enough of that Hussein," a white woman exclaimed to a television camera as she exited a voting booth in West Virginia.

This woman is like so many others who don't really know much about the first-term senator from Illinois. Those who follow politics more closely may have seen Obama's electrifying speech at the Democratic convention four years ago. Or watched his recent Philadelphia speech on race. Or read one of his best-selling books, in which he writes eloquently about who he is and what he believes.

But more people have only seen clips of Rev. Wright's sermons. Or heard other candidates attack Obama. Maybe they saw the interview in which Hillary Clinton was asked whether she believed Obama was a Muslim and answered, "No . . . not that I know of."

Many aren't sure they can trust Obama.

Building upon that skepticism, right-wing Web sites and talk radio have Rush-ed in to try to define Obama as one scary dude.

But there is too much at stake in this election - our security, our economy, our standing in the world, our quality of life on a planet with finite resources - to have it decided on the basis of rumor and innuendo.

Now that he is close to the Democratic nomination, Obama has to make a concerted effort to introduce himself to those millions of Americans who don't know much about him - or know only enough to dislike him.

When Obama was a community organizer in Chicago, he learned how to bridge the gap between his Ivy League education and those who lacked his advantages - the people he hoped to help.

After 15 months of sometimes exhilarating, often exhausting campaigning, Obama needs to reach deep down inside himself and do it again. Whether the skeptics are black, white or brown, Obama must make that connection, let people know who he is, without the clumsy gaffes that have marked his campaign.

He has to earn their trust.

Only then will the Muslim rumor be pushed to the side.

We know from experience that swift-boating can sink a candidacy. We need this next election to be based on facts, not fiction. *

Deborah Leavy is a regular contributor to the op-ed page and an associate member of the Daily News editorial board. E-mail her at deborah.opinion@gmail.com.