hit piece vs mudslinging

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. 

mudslinging

noun
  • An act of making damaging or spiteful remarks with the intent to discredit. 

  • Casting aspersions with intent to discredit. 

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