Original sentence: Obama is a Christian, but July 2008 polls showed that some Americans believed that he is Muslim or was raised Muslim (12% and 26%, respectively, in Pew and Newsweek polls)
Edited sentence: Obama is a Christian, but July 2008 polls showed that some Americans incorrectly believed that he is Muslim or was raised Muslim (12% and 26%, respectively, in Pew and Newsweek polls)