In my mind, there are three prerequisites to shift the Hoverton window. First, the speaker must have sufficient intellectual gravitas. Specifically, he must be able to generate a novel idea, that departs sufficiently from conventional wisdom, but also anticipates and preempts the most likely response. He must also have a reputation which warrants his ideas being taken seriously. Second, the speaker must have secure tenure-in-office. To challenge the status quo, you need decisional independence. No one can override your position, or worse, tell you to stand down after an uproar emerges. (Tenured academics and Article III judges are among the few people who fit in this category.) Third, the speaker must have courage. You must be willing to publicly articulate your principle, knowing full well that you will be savagely attacked from all corners. (Very few academics and Article III judges fit in this category.)