Both parties in the Senate elect whips. The term
"whip" comes from a fox-hunting expression—
"whipper-in"—referring to the member of the
hunting team responsible for keeping the dogs from straying
from the team during a chase. Established early in the 20th
century, the development of party whips coincided with the
evolution of party leaders in the Senate.
Democrat James Hamilton Lewis of Illinois became the
first party whip in 1913, and the Republicans established
their own whip position two years later. Traditionally
serving as assistant leaders, whips are mainly responsible
for counting heads and rounding up party members for votes
and quorum calls, and they occasionally stand in for the
majority or minority leaders in their absence. In 1970
Republicans began referring to their whips as assistant
leaders, but in 2003, they began using the whip title again.
Democrats used the title whip until 2003, when they began
calling the position assistant leader. In 2017 Democrats
created a new position of assistant leader, which is
separate from and ranks directly below the position of whip.