backbite vs run smear campaign

backbite

noun
  • One who engages in backbiting; a backbiter. 

verb
  • To attack from behind or when out of earshot with spiteful or defamatory remarks. 

  • To speak badly of an absent individual. 

  • To make spiteful slanderous or defamatory statements about someone. 

run smear campaign

How often have the words backbite and run smear campaign occurred in a corpus of books? (source: Google Ngram Viewer )