A power broker is a person who influences people to vote towards a particular client (i.e. elected official or referendum) in exchange for political and financial benefits. Power brokers can also negotiate deals with other power brokers to meet their aims.
Area of greatest influence
Power brokers can demand more benefits in closely contested areas and policies. They can play both sides and influence voters for the highest bidder. These brokers wield great influence over voters who may be dedicated to one issue that draws them into the electoral process but undecided on others. Hence, the brokers maintain their influence by denying loyalty to a political party or other political label. Modern examples of prominent figures include Henry Kissinger.
References
Power broker (politics) Wikipedia(Text) CC BY-SA