ballot box vs straw poll

ballot box

noun
  • The process or method of voting. 

  • A sealed box with a slit, into which a voter puts a completed voting slip. 

straw poll

noun
  • A survey of opinion or a vote that is nonbinding, unofficial, casual, or ad hoc. 

How often have the words ballot box and straw poll occurred in a corpus of books? (source: Google Ngram Viewer )