The problem with the unexpected is that, well, it’s unexpected.
A decade ago, some guy was running for Senate in Illinois as a Democrat. I’m not sure anybody thought he had a chance — after all, he’d already lost in a bid for a seat in the House — until the unexpected happened. In this case, details about the divorce of the front running Republican from his very pretty actress wife happened to be disclosed by the courts to the Chicago Tribune. And the details regarding his sex life were absolutely devastating.
The end result of this *ahem* unfortunate turn of events is that the Republican candidate was replaced by someone deemed “more electable,” and the underdog Democrat went on to win a seat in the Senate. Just a few years later, that man went on to become President of the United States.