Or she believed that a decades old allegation couldn't be proven one way or the other. I think she should have let the GOP know about it one way or the other, though. If the White House had known that this type of allegation was out there and selected him anyway, I would have had no problem with the Democrats going nuclear with this.
I think everyone on both sides here should be very, very careful making claims about what was really going on here, what people were thinking, and what really happened 30 years ago. I understand why conservatives think it was a last minute political manouver and attempt at character smearing, but that is not the only way to read it, and the popular Democratic narrative about what happened is even uglier. This type of situation is why each side thinks the other is not just wrong, but evil. Both sides mishandled this, and the midterm election is going to come down to which one is angrier in the aftermath.