Why do you find it ridiculous?
He is determined, he has resolve[ can decide on a course of action] , and he is courageous.
Using dictionary entries without considering the full context and background to the text can lead to confusion. The use of these three terms provide a rounded view of McCain's character that simply would not come over if all she had said was that he was daring or that he was hard.
This is not a negative criticism, but a suggestion that when you read English, remember that it is the whole sentence/paragraph that matters, and not simply the words within it. They can and do change their meanings within the context.
nb sheer in this context = nothing but; absolute