Final answer:
A member of Congress that assists party leaders by pressuring other members to support the leaders' positions is known as the party whip.
Step-by-step explanation:
A member of Congress who assists party leaders by exerting pressure on members to support the leaders' positions is called the party whip. The whip's job is to enforce party discipline, making sure that members of their party vote according to leadership's strategy. Whips often have to maneuver and sometimes use incentives to ensure that party members are in line with the proposed legislation. The majority and minority parties have their respective whips depending on the composition of Congress.