The media are calling this a "gaffe," but it's not so much a gaffe as a sort of cultural disconnect: it's commonly held among Evangelicals that separation of church and state doesn't appear in the constitution, that the concept is a distortion of the founders' intent created later by the liberal courts. I don't think this a case of mere ignorance.
i had the same thought when i watched the video, which is why i was surprised that everyone was focusing on the first amendment/separation of church and state bit. everyone seems to be skipping over (& indeed, the video posted in the first post has edited out) the part where she showed off her ignorance of other
parts of the constitution.
o'donnell was asked about the tea partiers' movement to repeal the 14th, 16th, & 17th amendment. she had to ask the questioner to "remind" her of what the amendments were. she had an answer for the 17th, but had no idea what the others were.
christine o'donnell wrote:
i’m sorry i didn’t bring my constitution with me. fortunately senators don’t have to memorize the constitution. can you remind me of what the other ones are?
he told her what the 14th was, then said "i think you should know what the 16th amendment is" -- & she gave him a blank stare, so he told her that one too.