How are the speaker’s characteristics important in successful public speaking?

In public speaking the speaker must has his credibility either initial or acquired. The initial credibility that refers to the speakers image or perception with the audience that my be the position of the speaker (rank), communicators good will among audience that will motivate the listeners to listen, expertise, image like identification power or referent power and the last the morality or fairness to the audience. Second comes the style of the speaker, his tone, speech delivery, dress and body language.