“The survey shows that a significant number of Americans would be reluctant to vote for a well-qualified candidate if he or she were a member of a particular religious group, especially a Muslim (38%). But many more express reservations about voting for a candidate without religion than one with a specific faith (52%). In all, 64% of Americans admit that a candidate’s religion, or lack thereof, could lead them to vote against a well-qualified candidate from their own party …
.. asked if there are ‘any reasons’ not to vote for a candidate with a particular religious affiliation if he or she were nominated by the respondent’s preferred party … [41%] say there are reasons why they would not vote for an atheist — far more than say that about a Muslim, an evangelical Christian, a Catholic or a Jew.
Atheism is a particular concern for white evangelical Protestants and African-Americans — majorities of each say there are reasons why they might not vote for an atheist if one received their party’s presidential nomination.”
Religion and Politics: Contention and Consensus (Pew Forum on Religion and Public Life)