By rule, the Presiding Officer gives the Majority Leader priority in obtaining recognition to speak on the floor of the Senate. The Majority Leader customarily serves as the chief representative of their party in the Senate, and sometimes even in all of Congress if the House of Representatives and thus the office of Speaker of the House is controlled by the opposition party.
The Assistant Majority and Minority Leaders of the United States Senate (commonly called Senate Majority and Minority Whips) are the second-ranking members of each party's leadership. The main function of the Majority and Minority Whips is to gather votes on major issues. Because they are the second ranking members of the Senate, if there is no floor leader present, the whip may become acting floor leader. Before 1969, the official titles were Majority Whip and Minority Whip.