The president's religion, like his place of birth, has been the subject of Internet-spread rumors and falsehoods since before he began his presidential campaign, and the poll indicates that those rumors have gained currency since Obama took office. The number of people who now correctly identify Obama as a Christian has dropped to 34%, down from nearly half when he took office.

The poll, released Thursday by the Pew Forum on Religion & Public Life, is based on a survey of 3,003 adults conducted before the Manhattan mosque uproar last week.

White House officials expressed dismay over the poll results, blaming "misinformation campaigns" by the president's opponents.

Among those who say Obama is a Muslim, 60% say they learned about his religion from the media, suggesting that their opinions are fueled by misinformation. Among specific media sources, television (at 16%) is mentioned most frequently.

But the shifting attitudes about the president's religious beliefs could also be the result of a public growing less enamored of him and increasingly attracted to labels they perceive as negative.

In the Pew poll, 41 % disapprove of Obama's job performance, compared with 26 % disapproval in its March 2009 poll.

The view that Obama is a Muslim is more widespread among his political opponents than among his backers. Specifically, more than a third of conservative Republicans now say Obama is a Muslim, nearly double the percentage saying so early last year. More Independents, too, believe the president is Muslim: 18 % say he is a Muslim, up eight percentage points.

But even among many of his supporters and allies, less than half now say Obama is a Christian. Among Democrats, for instance, 46% say Obama is a Christian, down from 55% in March 2009.

Those numbers come as Obama and other Democrats try to minimize potential fallout from the president's remarks on Friday about the Islamic center in New York.

A new Time-SRBI poll found that 61 % of Americans oppose building the center. Nearly twice as many people said the center, and the mosque inside it, would be an insult to 9/11 victims than said it would be a symbol of religious tolerance.

In the Time poll, 25% say most Muslims in the United States are not patriotic Americans. But the survey also indicates that the public's opposition to the center may be more complicated than just anti-Muslim sentiment. Fifty-five percent said they would accept a Muslim community center and place of worship two blocks from their own home.

More than a year and a half into his presidency, a plurality of the public says they do not know what religion Obama follows.

The Pew poll found that beliefs about Obama’s religion are closely linked to political judgments about him. Those who say he is a Muslim overwhelmingly disapprove of his job performance, while a majority of those who think he is a Christian approve of the job Obama is doing. Those who are unsure about Obama’s religion are about evenly divided in their views of his performance.