oppositionist

opposition +‎ -ist

oppositionist (plural oppositionists)

1. A person who opposes; especially a member of an official opposition
   • 1944, Morris Allison Bealle, Washington Squirrel Cage, page 9:

     They felt that the fellow was a quockerwodger rather than a politician, an againster rather than a true American, an oppositionist in fundamental things rather than a sincere patriot.

   • 2015, Rosemary Sullivan, Stalin's Daughter, →ISBN, page 137:

     I see your marriage as a move to establish links with the oppositionist Russian intelligentsia.

• oppositionism