powerbroker

or pow·er bro·ker

[ pou-er-broh-ker ]
/ ˈpaʊ ərˌbroʊ kər /

noun

a person who wields great political, governmental, or financial power.

Origin of powerbroker

An Americanism dating back to 1960–65; power + broker

British Dictionary definitions for power broker

power broker

noun

a person with power and influence, esp one who operates behind the scenes