leading man vs principal participant

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 participant

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