The Washington Post covered her most recent debate, wherein it became clear that she did not understand that separation of church and state is part of the First Amendment:

Republican Senate nominee Christine O’Donnell of Delaware on Tuesday questioned whether the U.S. Constitution calls for a separation of church and state, appearing to disagree or not know that the First Amendment bars the government from establishing religion.

The exchange came in a debate before an audience of legal scholars and law students at Widener University Law School, as O’Donnell criticized Democratic nominee Chris Coons’ position that teaching creationism in public school would violate the First Amendment by promoting religious doctrine.

Coons said private and parochial schools are free to teach creationism but that “religious doctrine doesn’t belong in our public schools.”

“Where in the Constitution is the separation of church and state?” O’Donnell asked him.

When Coons responded that the First Amendment bars Congress from making laws respecting the establishment of religion, O’Donnell asked: “You’re telling me that’s in the First Amendment?”

Her comments, in a debate aired on radio station WDEL, generated a buzz in the audience.

“You actually audibly heard the crowd gasp,” Widener University political scientist Wesley Leckrone said after the debate, adding that it raised questions about O’Donnell’s grasp of the Constitution.

This woman wants to be a Senator. Seriously.

Update: TalkingPointsMemo has video.