hit piece vs smear campaign

hit piece

noun
  • A published article or post aiming to sway public opinion by presenting false or biased information in a way that appears objective and truthful. 

smear campaign

noun
  • An effort to damage or call into question someone's reputation, by propounding negative propaganda. 

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