Early polls rarely paint an accurate picture of the race, especially in wave years, either way. If we look at 2014, right now you would have thought Peters was going to lose in Michigan and Pryor was going to win in Arkansas.
Hagan and Begich were also +20 approval rating this time in 2013.
Carter, Dukakis and Bush II were also ahead by 15-20 points one year before their election as I'm sure you know 
If Toomey is not inevitable (which he isn't), Hillary will be neither 
Taking things in a vacuum and looking for a pattern is asking to be wrong. I bet you were part of the crowd that thought Romney was going to win because the Redskins lost the Sunday before election day.
Carter and Bush II had national tragedy rallies on their numbers. 1987 had a stock market crash and recession that hurt Bush I. They weren't genuinely what their numbers were at this point.
We are in a low point for Hillary Clinton, where she is getting attacked by the media religiously.
