leading man vs principal character

leading man

noun
  • A man who does or can play the lead role in a movie, play or other production; a person who frequently plays such roles. 

  • The type of conventionally handsome and approachable man who is perceived as being capable of playing male lead roles in movies or other productions. 

principal character

How often have the words leading man and principal character occurred in a corpus of books? (source: Google Ngram Viewer )