They are complete sentences. Both have an independent and dependent clause.
Hello. You did not submit the text to which this question refers, which makes it impossible for it to be answered. However, I will try to help you as best I can.
The only way to answer this question is by reading the text it is related to. During this reading, there are two ways in which you can see how effective Powell's appeal is in relation to a two-party approach to political issues. The first way is to analyze the evidence that Powell used to justify his position. In that case, you must assess how far this evidence is consistent with reality and is capable of proving that Powell's opinion is relevant. The second way is to assess how much Powell's opinion is relevant to you and how much you agree with him. If you choose the second option, you will need to use your own evidence to justify your opinion.
