White evangelical Protestants and Republicans were the most likely to say Obama , who has an Arabic middle name, was a Muslim.
The researchers in their poll question asked:"Do you happen to know what Barack Obama's religion is?"
Nearly one in five white evangelical Protestants and 17 per cent of the Republicans who took part in the telephone poll of 1,308 adults, which was conducted by Pew Research from March 9-12, said they thought Obama was Muslim.
In spite of Obama being on record about his Christian faith and his well known association with a Chicago United church, opponents raised questions about Obama's religion during the contentious 2008 US Presidential campaign.
The debate over Obama's religion soon took to the Internet where Obama's campaign started its own website to address the religion issue.