Now, to answer your probable first question: fivethiryeight.com is an organization that takes national polls and compiles all data to make very VERY accurate predictions. They correctly predicted not only who won in 2012, but who would win each of the individual 50 state as well with 100% accuracy.
They stated the only time somebody ever blew this sort of lead was Mike Dukakas. Not to say its impossible to happen, but is unlikely at this point.