I find the claim preposterous, and so these numbers just as shocking. From Tobin Grant’s article at CT…

President Obama told Christianity Today in 2008, “I am a Christian, and I am a devout Christian.” According to a new Pew Forum survey, only a third of Americans believe him. This is only slightly more than the 18 percent who think he is a Muslim. Among evangelical Christians, 29 percent believe Obama is a Muslim, but only 27 percent think he is a Christian. 

Since March of last year, the percentage of Americans who think Obama is a Muslim has increased from 11 to 18 percent, while the percentage who think he is a Christian dropped from 48 to 34 percent.