President Barack Obama, who faces a false but growing perception that he is a Muslim, isn't the first president to encounter claims that his faith isn't what he says it is.
Thomas Jefferson, an Anglican who viewed God as a distant, impersonal creator, was accused of apostasy in the 1800 race. One newspaper wrote that under such heretical rule, "murder, robbery, rape, adultery and incest will be openly taught and practiced."
The faith of Abraham Lincoln, a Baptist-turned-skeptic who later found comfort in Calvinism, remains hotly debated by historians to this day.
Lincoln, "who was a very religious person but not a member in any particular church, received a lot of criticism from other Protestants because he wasn't devout enough," said John Green, senior research adviser for the Pew Forum on Religion and Public Life.
Pew's July poll found that 18 percent of Americans believe that Mr. Obama is a Muslim, up from 11 percent in March. Another 43 percent don't know what his religion is, despite campaign headlines about his membership in the United Church of Christ.
But most disputes about presidential faith differed from the misinformation about Mr. Obama. Some presidents or candidates were denounced because they indeed belonged to an unpopular faith, such as John F. Kennedy (Catholic) in 1960 or Mitt Romney (Mormon) in 2008.
The broadsides against Jefferson and Lincoln accused them of being less-than-faithful to popular faiths.
The claims about Mr. Obama most closely parallel a dispute about Dwight D. Eisenhower. The commander of Allied forces in Europe during World War II was the son of a Jehovah's Witness. His mother practiced that faith until her death in 1946, though his father left it after the world failed to end as predicted by 1915.
The Witnesses are rarely mentioned in his biographies. Some scholars believe that Eisenhower's brothers deliberately obscured his religious upbringing. There is no evidence that he was ever a committed Witness. He was a soldier and a president, while Witnesses were forbidden to serve in the military, salute the flag or vote.
Nevertheless, political opponents tried to connect him to his mother's faith, pointing out that he was sworn in using a Witness-approved Bible that she had given him in 1915. He was accused of being "an anti-Christian cultist" and a "foe of patriotism."
Few people swallowed that because of his status as a war hero, Mr. Green said. "But one way in which this is very similar [to Mr. Obama] is that you have individuals trying to associate the president with an unpopular group," he said.
Although the Jehovah's Witness theology has always been controversial, they were excoriated during World War II due to high-profile cases of refusal to serve in the military or to say the Pledge of Allegiance, he said.
In this era, Muslims are unpopular. In a 2007 Pew poll, 45 percent of adults said they would hesitate to vote for a Muslim. And the current debate over an Islamic center near Ground Zero shows that many Americans strongly associate Islam with terrorism, he said.
The perception that Mr. Obama is a Muslim is tied to opposition to his policies. "A very large percentage of the people who think that President Obama is a Muslim have negative views of his job performance," Mr. Green said.
Sixty percent of those who believe he's a Muslim say they learned that from "the media." While they may mean certain websites or radio shows, 10 percent said that they had heard Mr. Obama call himself a Muslim. Mr. Green suspects that they were just confused.
"He does talk about Islam from time to time. So, in the limited way that people process information, they may have misunderstood what he was saying. It fits with the statistic that 43 percent just don't know what his faith is," Mr. Green said.
The idea that he is or was a Muslim is promoted by sites such as www.stop-obama.org. The arguments are based on the premise that his father and step-father were at least nominal Muslims.
One claim is that the son of a Muslim father is automatically a Muslim. The other derives from the fact that he lived in Indonesia from the ages of 6 to 10. The theory is that, when he went to mosque with his step-father, he recited prayers including the profession of faith that "there is no god but God" and Muhammad is his messenger.
The Rev. Franklin Graham, a prominent evangelical, gave credence to such arguments on CNN, though he acknowledged that the president professes Christianity.
"He was born a Muslim. His father was a Muslim. The seed of Islam is passed through the father like the seed of Judaism is passed through the mother," he said.
That's not true, said Jonathan Brown, a professor at the Prince Alwaleed bin Talal Center for Christian-Muslim Understanding at Georgetown University.
"Being Muslim has nothing to do with descent or race," he said.
Outsiders may be confused because a child raised in a Muslim family doesn't go through a conversion or initiation ceremony similar to baptism or confirmation, he said.
Technically, all that's required to become a Muslim is to profess that there is no god but God and Muhammad is his messenger. But nothing that a child says or does before puberty counts, Mr. Brown said.
Even if 10-year-old Barack had made a pilgrimage to Mecca, "it wouldn't have counted. He would have had to do it again when he was older," he said.
If he had sincerely adopted Islam as a teen or young adult, "it doesn't matter, because he became a Christian. If you convert to another religion, then you're not Muslim."
Mr. Obama answered an altar call at Trinity United Church of Christ in Chicago and professed faith in Jesus. Stephen Mansfield, the evangelical author of "The Faith of Barack Obama" disagrees with Mr. Obama's liberal expression of Christianity, but recently blogged that, "Yes, he believes that Jesus is the Son of God. Yes, he believes that Jesus died on a cross for the sins of the world. Yes, he believes that God raised Jesus from the dead again."
Muslims don't believe any of that. The strictest clerics would say that someone had left the faith for merely visiting a church, Mr. Brown said.
But that leads to claims that Mr. Obama is an apostate Muslim who will, therefore, be killed for rejecting the faith of his fathers.
Such arguments are false, Mr. Brown said. Real Muslims don't believe Mr. Obama ever was a Muslim. Nor do they routinely kill ex-Muslims, he said.
Although Muhammad appeared to invoke the death penalty for apostasy, that's not how major Islamic scholars understand his words today, Mr. Brown said. The early Islamic community was both a political and religious entity, and mainstream scholars say that execution was for treason against the state, not for leaving the faith, he said.
While Westerners hear of people killed for renouncing Islam, those cases are driven by tribal identity and dysfunctional family dynamics, he said.
"If you belong to a really strong Muslim family and you apostacize, your family will be very upset and might disown you -- although they might accept you again once you have their grandkids. If you have a really, really awful family, maybe one of your cousins will kill you. That's very rare," he said. "People change religions all the time."
Rabbi Alvin Berkun believes something more subtle than bloggers and more sinister than ignorance is at work in the polls about the president's faith.
"I don't think people would be saying this if he were not a black president," he said.
"It's very sad. We had thought that we had this major breakthrough on race, and now people are holding him up in a way that says, 'He's not one of us.'"
The rabbi emeritus of Tree of Life Congregation in Squirrel Hill is chairman of the National Council of Synagogues, which represents Conservative Judaism in formal dialogue with non-Jewish faith groups.
"It's painful to see the term Muslim used as an insult," Rabbi Berkun said.
"If he were a Muslim, my answer would be, 'So what?' as long as he was living by the tenets of that faith that are wholesome and wonderful."
From Babylonian exile until the modern State of Israel in 1948, Jews have rarely lived under Jewish rule. They long ago learned to accept governors who don't share their faith, he said.
"We have close to 2,000 years of experience on exactly that issue. Sometimes our experience has been good, it's usually been bad. But we have coped," he said.
The medieval Jewish philosopher Moses Maimonides, who served in the court of a Muslim king, wrote of qualities that a ruler of any faith should have, he said. These included a dispassionate interest in justice, tempered by mercy and compassion.
Some positive poll data on faith and politics shows that anti-Semitism has faded, Mr. Green said.
"People say they would feel comfortable voting for a well-qualified Jew for president," he said. "When Joe Lieberman ran for vice-president, I was one of the pollsters who looked long and hard to see if we could find evidence of anti-Semitism. We really couldn't."
Anti-Catholic prejudice faded during the Kennedy presidency, he said. And though 25 percent of Americans expressed reservations about voting for a Mormon in 2007, 66 percent said it would make no difference. The biggest objection wasn't to Muslims but to atheists, who 61 percent of Americans would hesitate to vote for.
Loud objections to Muslims in government aren't always widely shared, Mr. Green said.
When Rep. Keith Ellison, D-Minn., became the first Muslim elected to Congress, some conservative Protestants objected to his choice to take the oath of office on a Quran.
But polls "found that most people didn't care. They said, 'Well, if he's a Muslim, it's a good thing he's being sworn in on the holy book of his religion. They thought that made sense," Mr. Green said.
Ann Rodgers: firstname.lastname@example.org or 412-263-1416.