I argued that the speaker's credibility must be built and established in each speech; that what the speaker did or said before did not matter.
It is important to realize that nowadays there are three different types of credibility. First is initial credibility, then derived and finally terminal credibility. Initial credibility is the credibility the speaker has before he or she says a word, the credibility at the start of the speech. Derived credibility is how it increases or decreases during the speech itself. It is important to note that this can wax and wane during the speech. Terminal credibility how credible the audience perceives the speaker to be at the end of the speech.
If you are trying to convince someone of something, it is important that you think about this aspect of things. What is your initial credibility? What can you do to increase that credibility during your presentation to make sure you finish with strong terminal credibility. Only if your terminal credibility is high will you be able to change the mind of some people in your audience. Not many students or speakers actually think about this aspect. If you do, it will lead to you giving much stronger presentations.