Again, you need the audio, and in this case full-screen video, to get her meaning. As she says, "That's in the First Amendment," she stares at Coons with a look of contemptuous amusement. (You can see her expression more clearly in this video, about seven minutes in.) Then she grins knowingly at somebody in the audience. She thinks Coons has just embarrassed himself.
O'Donnell isn't a total ignoramus. On some particulars of the First Amendment, she seems better briefed than Coons. Thirty-two minutes into the debate, she catches Coons with a pop question:
O'Donnell: Can you name the five freedoms guaranteed in the First Amendment?
Coons: I think the very first provision of the First Amendment is that the government shall make no establishment of religion. And before we get into a further debate about exactly which of us knows the Constitution better, how about we—
O'Donnell: No, I'm just asking: Can you name the five freedoms guaranteed in the First Amendment?
Coons: —how about we get the panel asking our questions today.
Obviously, Coons wasn't prepared to answer the question. Presumably, O'Donnell was. (The five freedoms are religion, speech, press, assembly, and petition.) My guess is that she had this question written down on the notes she brought to the debate, which you can see spread out before her in the video. But there's a difference between his ignorance and hers. He was asked to fill in a blank. Lacking confidence that he knew the correct answers, he refused to guess. (We don't know how many of the five freedoms he could have named; we just know that he doubted he could guess them all.) She, on the other hand, was repeatedly presented with a correct answer and repeatedly rejected it. She showed tremendous confidence that what was true was false.
At no point in the debate did O'Donnell offer any of the sophisticated church-state arguments her defenders now attribute to her. She didn't quote the establishment clause for the same reason that Coons didn't quote the five freedoms: because she couldn't. Not until after the debate—apparently at the direction of her campaign team—did she tell National Review, "What our constitution prevents is … government establishing a religion, but it also says that it won't prohibit free exercise thereof." She noted that Coons "forgot to quote" the part about prohibiting free exercise. But Coons did quote the part about government establishing religion. He quoted it twice. And each time, she responded with wry disbelief.
The disturbing thing about this episode isn't O'Donnell's ignorance of the First Amendment. As her damage-control interview makes clear, that ignorance has now been repaired. What's disturbing is the bemused confidence with which she mocked the truth. It's the same confidence with which she dismisses evolution, claims that America has gone socialist, and asserts that "American scientific companies are cross-breeding humans and animals and coming up with mice with fully functioning human brains." Ignorance is temporary, but imperviousness is forever.