Words do matter and few presidents knew this better than JFK (who of course also understood that rhetorical power has its limits).
How JFK came up with his memorable words and why they matter -- from "ask not" to the Cuban Missile Crisis -- is the subject of this US News and World Report excerpt of my book, White House Ghosts: Presidents and Their Speechwriters.
UPDATE: I should note -- happily -- that in addition to be a great news magazine, US News and World Report is also my employer.
Well, looks like I was mistaken. I was talking in an empty room!
I can already hear the complaint. Yes, of course, eventually he did use speech writers as of course his schedule made necessary. But Reagan before the speech writers was a wonderful writer. And his respect for the dignity of individuals and his wonderful sense of empathy made him a very adept editor of his speech writers, bringing their wordsmithing back down to earth, giving it the tone of real speech.
He was a great good man. But don't take my word for it. The Reagan documents are wonderful to read, full of stories about life.