influencer

[in-floo-uh n-ser]

noun

a person or thing that influences: The most powerful influencer of beliefs is direct experience.
a person who has the power to influence many people, as through social media or traditional media: Companies look for Facebook influencers who can promote their brand.

Origin of influencer

First recorded in 1660–70; influence + -er¹

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Huston writes in the book that Ara Gallant was "an influencer, a mentor, an advisor, a director, a comrade in arms."
The Man Who Created Disco Beauty
Isabel Wilkinson
March 31, 2010

As an influencer of legislatures, he stands easily first in ability and achievement.
The Boss and the Machine
Samuel P. Orth