Answer:
It comes from a hunting expression, but the term has been used to refer to the position of an assistant to the party leaders who help get votes.
Explanation:
Whips are responsible for rounding up party members to vote for a bill and have the majority they need. Sometimes however, the party doesn't have a majority in the Senate or House of representatives. The role of the whip is to get votes from the opposing party members or independent members. At times, they can fill in for majority or minority leaders when these are absent.
