single-issue

English Wikipedia has an article on:

single-issue politics

Wikipedia

single-issue (comparative more single-issue, superlative most single-issue)

1. (chiefly politics) Concerned with one essential policy area or idea.

   single-issue party

   • 1982, Mancur Olson, The Rise and Decline of Nations, Yale University Press, →ISBN, page 8:

     The concern about ungovernability in the United States often takes the form of complaints about “single-issue” politics and the limited influence and discipline of American political parties.

• single-issueism