Polls
For a more reliable poll (as reliable as polls get, anyway) try this one.
The entire poll can be found here, and should probably be bookmarked for when this crap comes up again. And it will.
The question on evangelicism is on page 39:
"Some people think of themselves as evangelical or born again Christians. Do you ever think of yourself in either of these ways?"
National Poll (general population): Yes, 28%. No, 70%. DK, 2%.
Tea Party Backers: Yes, 39%. No, 58%. DK, 2%.