By JIM RUTENBERG

The most persistent falsehood about Senator Barack Obama’s background first came out in 2004, just two weeks after the Democratic National Convention speech that helped set him on the path to his presidential candidacy: “Obama is a Muslim who has concealed his religion.”
That statement, contained in a press release, spun a complex tale about the ancestry of Mr. Obama, who is Christian.
The press release was picked up by a conservative Web site, FreeRepublic.com, and spread as others elaborated on its claims in e-mail messages, Web sites and books.
Until this month, the man who is credited with starting the cyber-whisper campaign was a secondary character in news reports. But a recent appearance on the conservative Fox News Channel thrust the man, Andy Martin, into the spotlight.
The Fox News program al lowed Mr. Martin to assert falsely and without challenge that Mr. Obama had once trained to overthrow the government . The show’s producer said Mr. Martin was clearly expressing his opinion and not necessarily fact.
An examination of legal documents and election filings, reveals Mr. Martin to be a man with a history of scintillating if not always factual claims. He has left a trail of animosity - some of it provoked by anti-Jewish comments - among political leaders, lawyers and judges in three states over more than 30 years.
He is a law school graduate, but his admission to the Illinois bar was blocked in the 1970s after a psychiatric finding of “moderately severe character defect manifested by welldocumented ideation with a paranoid flavor and a grandiose character.”
Though he is not a lawyer, Mr. Martin is a prodigious filer of lawsuits. He has made unsuccessful bids for public office for both major parties in three states, as well as for president in 1988 and 2000. When running for president in 1999, he aired a television advertisement in New Hampshire that accused George W. Bush of using cocaine. He also prepared to run as a Democrat for Congress in Connecticut, where paperwork for one of his campaign committees listed as one purpose “to exterminate Jew power.”
In court papers, Mr. Martin has impugned Jews. A motion he filed in a 1983 bankruptcy case called the judge “a crooked, slimy Jew who has a history of lying and thieving common to members of his race.” In a motion in 1983, he wrote, “I am able to understand how the Holocaust took place, and with every passing day feel less and less sorry that it did.”
Based in Chicago, Mr. Martin, 62, now identifies himself as a writer who focuses on his anti-Obama Web site and press releases. He did not dispute his influence on the Obama rumors. “Everybody uses my research as a takeoff point,” he said, adding, however, that some take his writings “and exaggerate them to suit their own fantasies.”
Mr. Obama was raised mostly by his white mother, an atheist, and his grandparents, who were Protestant, in Hawaii. He hardly knew his father, a Kenyan from a Muslim family who variously considered himself atheist or agnostic, Mr. Obama wrote. For a few years in childhood, he lived in Indonesia with a stepfather he described as loosely following a liberal variety of Islam. Mr. Obama wrote in his memoir that in Indonesia he attended a Catholic school where he was taught about the Bible and a public school, open to all religions, where he was taught about the Koran.
Theories about Mr. Obama’s background have taken on a life of their own. But independent analysts seeking the origins of the cyberspace attacks point to Mr. Martin’s first press release, posted on the Free Republic Web site in August 2004.
“What he’s generating gets picked up in other places,” Danielle Allen, a professor at the Institute for Advanced Study at Princeton University in New Jersey who has investigated the e-mail campaign, said of Mr. Martin, “and it’s an example of how the Internet has given power to sources we would have never taken seriously at another point in time.”
Mr. Martin denied some statements against Jews attributed to him in court papers, blaming malicious judges for inserting them.
He said he had at least come to “accept” Mr. Obama’s word that he had found Jesus. His intent, he said, was only to educate.