Final answer:
The evidence showing McCain's determination is that he persisted in his political career despite setbacks, displaying resilience against various challenges and controversies.
Step-by-step explanation:
Among the presented options, the piece of evidence that supports the idea that McCain is a determined individual is C) He persisted in his political career despite setbacks. McCain's resilience in the face of challenges throughout his career, including his endurance of daily beatings as a POW for refusing to slander the United States, his principled stance on issues like torture and campaign finance reform, and his continuation in politics even after controversies and association with the troubled legacy of the Bush administration, all demonstrate his determined character.