noun
kingmaker
KING-may-ker/ˈkɪŋmeɪkər/
A powerful person who helps determine who becomes a leader without taking the role.
The retired governor remains a kingmaker, deciding which candidate wins support.

Etymology
A kingmaker “makes” kings by helping put them in power. The name originally referred to the Earl of Warwick’s role in elevating and restoring monarchs; the selected sense extends that role to leaders generally.
In context
when the labor movement was a real kingmaker
More examples
- Neither candidate can win without the support of the local kingmaker.
- The billionaire acts as a kingmaker by funding his preferred candidate.
- Several longtime board members are kingmakers in the search for a CEO.
Forms
kingmaker · kingmakers
kingmaking noun — The exercise of influence in choosing leaders.
Similar words
- power broker
- Arranges political deals but does not necessarily determine leadership.
- backer
- Supports a candidate but may not control the outcome.