Here's how the elections get cancelled

Somehow, someway Trump will be prevented from continuing in the election. It may be as simple as the RNC dumping him which would then preclude him from running as a third-party candidate because deadlines for him to appear on the ballot in all 50 states would have passed.

Then, Hillary will have a major "medical" incident that will prevent her from continuing.

Yes, there are rules for what happens within the parties if a candidate drops out for whatever reason but in the confusion of both candidates leaving the race at the last moments, Obama will issue yet another of his executive orders. In it, he will declare a national emergency -- the magic key he needs to unlock a plethora of special powers that, among other things, eliminate Congress and the Sumpreme Court as the other branches of government. With these powers, he will become a dictator practically overnight. And no, the military won't stop him. Many have thought his firing of top brass over the years was about weakening the military against the Islamic threat but that's not what it was about. He simply wanted to put in his own puppets for exactly this moment.