From The Gallup Poll:
PRINCETON, NJ — The majority of Republicans in the United States do not believe the theory of evolution is true and do not believe that humans evolved over millions of years from less advanced forms of life. This suggests that when three Republican presidential candidates at a May debate stated they did not believe in evolution, they were generally in sync with the bulk of the rank-and-file Republicans whose nomination they are seeking to obtain.
Independents and Democrats are more likely than Republicans to believe in the theory of evolution. But even among non-Republicans there appears to be a significant minority who doubt that evolution adequately explains where humans came from.
The data from several recent Gallup studies suggest that Americans’ religious behavior is highly correlated with beliefs about evolution. Those who attend church frequently are much less likely to believe in evolution than are those who seldom or never attend. That Republicans tend to be frequent churchgoers helps explain their doubts about evolution.
The data indicate some seeming confusion on the part of Americans on this issue. About a quarter of Americans say they believe both in evolution’s explanation that humans evolved over millions of years and in the creationist explanation that humans were created as is about 10,000 years ago.
They also break the results down by church attendance:
(via Respectful Insolence)