duel vs political opposition

duel

noun
  • Any battle or struggle between two contending persons, forces, groups, or ideas. 

  • Arranged, regular combat between two private persons, often over a matter of honor. 

  • Historically, the wager of battle (judicial combat). 

verb
  • To engage in a battle. 

political opposition

noun
  • Actions by one political group against another political group, either by using governmental power or by popular actions such as protests; generally, disagreement in politics. 

  • A recognized political party or group of parties in multiparty political systems that is present in Parliament or some other legislative body and does not control the floor (usually due to being in the minority). 

  • An unrecognized political party in a one-party state. 

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