power broker definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a person who has power and influence, esp. one who operates unofficially or behind the scenes as an intermediary
also written powerbroker
power broker definition by American Heritage Dictionary
A person who exerts strong political or economic influence, especially by virtue of the individuals and votes he or she controls.