An effective communicator need not be the most eloquent communicator. When it comes to his speaking time, if Bush is asked a question about tax policy, he should summarize his tax proposal and explain how it would contribute to the nation's growth. In other words, he should focus on policy. Given how few of the other candidates have devoted much time to substance, he has had a rich opportunity to stand out. So far, he hasn't taken advantage of it. If one reads his website, he has some serious ideas that he could easily lay out. Most of the nation's voters almost certainly do not visit candidates' websites to look for details, hence it is incumbent on the candidates to make their cases.
Tonight, he should forget Trump, forget Cruz, forget Rubio. He should strictly focus on where the U.S. is, what it needs, and how he would deliver it. He should get into some level of detail (major points) Let the others go after one another. My guess is that he won't. Just saying he has led successfully before isn't enough. Conveying how the combination of his leadership experience and his policy ideas will benefit the nation is what he needs to do.
Absolutely. Unfortunately, I don't believe the RNC understands this nor many of the pundits do (some of whom are cheerleading the two most anti-Establishment candidates). Trump and Cruz (but Trump to a much larger extent) are effectively rebranding the Party in a potentially damaging fashion. In the wake of Trump or Cruz led electoral defeat, it is possible that the Democratic Party could become the de facto national party. Over time, single party dominance leads to stagnation. Strong competition keeps things dynamic and allows for flexibility to change when circumstances require it. That kind of dynamism and flexibility could be lost if, let's say, Trump wins the nomination and is defeated in a near-nationwide landslide.