Poor delivery, it doesn’t get much play in rhetoric today. That’s one of the reasons I found the discussion of the physicality of delivery in Book III interesting.
Aristotle thought that delivery was acting and acting was an innate skill – maybe what Plato would call a knack. But Cicero disagreed; rather than import "the gesture of the stage" to oratory, he spent some time describing a basic body language for orators. From breathing to movement of arms and legs to eye movement, he's got tips for the novice rhetor. For "actions are the speech of the body".
Cicero does issue a note of caution concerning the use of gestures in delivery, noting that it is action which "moves", that is, affects, vulgar people and barbarians (III LIX). Actions demonstrate "the movements of the soul and thus are what ultimately influence people, especially the mob (III LIX). It's up to the orator to soften that power via the soul. That's where manners and morals come into play.
Now we have professional body language experts who usually get consulted by the press about politicians. And now it doesn’t seem that delivery gets much play these days.