Progressive vs leftish

Progressive

adj

  • Of or pertaining to such a party, its policies, or its membership. 

  • Belonging to or supporting a Progressive Party. 

noun

  • A member or supporter of a Progressive Party. 

leftish

adj

  • Leaning towards the political left. 

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