Conservative Republicans who believe President Barack Obama is a Muslim have more than doubled since 2008, according to a survey on religion and politics released on Thursday.

The Pew Research Center found that 34 percent of conservative Republicans now believe Obama, who is a Christian, is actually a Muslim, compared with the 16 percent that believed that in 2008. When moderate and liberal Republicans are included, the number who believed that the president a Muslim still nearly doubled from 16 percent in 2008 to 30 percent in 2012.

Among all voters, only 49 percent were able to correctly identify that the president is a Christian.

Sixty-five percent of those who incorrectly believed Obama is a Muslim were not comfortable with his religion. However, voters who knew that he is a Christian said they were comfortable with his religion by a margin of 82 percent to 12 percent.

At the same time, the number of voters who could correctly identify that presumptive Republican presidential nominee Mitt Romney is a Mormon had increased from 48 percent in November of 2011 to 60 percent in July of this year.

Seventy-five percent of Republicans who knew that Romney is a Mormon were comfortable with his religion, although only 50 percent of all voters believed Mormons are Christians. Sixty-seven percent of atheists identified Mormons as Christians, while only 33 percent of black Protestants and 43 percent of white evangelicals agreed with that assertion.

Photo: Flickr/The White House