The stubborn misperception among a wide swath of the population that President Obama is not a Christian has laid bare a host of difficult realities in the United States; from the notion that being a Muslim would hurt him with voters to whether the perception is fueled by his race.
On top of the ongoing fracas over an Islamic center planned near Ground Zero, it also exposes a religious barrier in U.S. politics that could prove more persistent than gender or race.
A president's faith matters to many Americans. It was seen as a milestone when John F. Kennedy, a Catholic, was elected president after he went to great lengths during the campaign to insist that his religion would not affect his policies.
The Constitution enshrines clearly that religion should not matter.
"... no religious test shall ever be required as a qualification to any office or public trust under the United States," according to Article Six.
But Kennedy remains the only Catholic to attain the post.
And a 2007 Pew survey found that 45 percent of Americans said they would be less likely to vote for a Muslim. 61 percent said they would be less likely to vote for an atheist. Only 25 percent said they would be less likely to vote for a Mormon candidate. Sixteen percent said they would be less likely to vote for an Evangelical and 11 percent would be less likely to vote for a Jewish candidate. Far fewer, six percent, said they would be less likely to vote for someone who is black.
Bobby Jindal is of South Asian descent and is the Republican governor of Louisiana. But he is also Catholic, a much more prevalent religion in Louisiana than the Hinduism of Jindal's parents.
Nikki Haley, a Republican, stands a good chance of being elected as the first female governor of South Carolina. She too is a convert to Christianity, a fact the former Sikh makes clear on her website.
"'The pigment of Obama's, Jindal's or Haley's skin does not seem to matter,' goes the popular narrative, but Christian faith is a foregone criterion for electability," Aseem Shukla, co-founder of the American Hindu Society, wrote in Newsweek. "A religious litmus test is clearly in play."
For many Americans, however, a candidate's faith is extremely important because it can give a hint to his or her beliefs, said Tom Minnery, senior vice president for Focus on the Family, an evangelical organization that promotes its causes in politics.
"It is Important for candidates to have a biblical world view," Minnery said. "A view that says there is right and wrong and good and evil and the rights come from a creator. And that is God, not government. Those are key beliefs."
Some founding fathers, such as Thomas Jefferson, had complicated relationships with religion that would be more difficult for voters to stomach today.
"Question with boldness even the existence of God; because if there be one, he must more approve the homage of reason, than that of blindfolded fear," Jefferson wrote to his nephew.
"Think if this guy ran for president today and someone googled him," said Sean Faircloth, executive director of the Secular Coalition of America, which advocates for a strict separation of church and state and encourages acceptance of nontheists.
Three Presidents, Jefferson, Abraham Lincoln and Andrew Johnson, were not affiliated with a sect of Christianity. But Lincoln often quoted the Bible and referred to God.