Hillary Still Ahead

Something is definitely going on with Hillary's campaign. This morning she was getting 61.1, now she's getting 59.9. A small drop, for sure, but she was pulling over 70 only a week ago. Obama, on the other hand, now has odds at 1 in 3, which is about a 20 point increase in his odds of winning from a week ago. What happened this last week to make the winds change so dramatically? I haven't heard anything; it seems like it came out of nowhere. Is this the Opray Winfrey endorsement? I wonder if anyone has done an event study on that, actually.