Answer:
Some leaders are just as effective behind the scenes.
Step-by-step explanation:
The main claim of the author in the given passage is the importance of being a competent public speaker for a person to be a leader. This claim is supported by his opinion that leaders need to be effective public speakers for "[they need] to communicate their ideas in big groups of people and [. . .] rally supporters with engaging oration."
And in the counterclaim, the author states that "some leaders are just as effective behind the scenes, working effectively without recognition". This is contrary to the claim that leaders should be effective public speakers.