Members of each major party meet in closed sessions known as party conferences (or party caucuses) to elect floor leaders, make committee assignments, and set legislative agendas. The Democratic floor leader serves as chair of the party conference, while the Republican party separates the positions, electing a chairperson for the party conference, apart from the floor leader.
----------------------------------------------------------------
| Senator | Term | |
|---|---|---|
 | Hale, John P. (NH) | ended 1862 |
 | Anthony, Henry B. (RI) | 1862-1884 |
 | Sherman, John (OH) | 1884-1885 |
 | Edmunds, George (VT) | 1885-1891 |
| Sherman, John (OH) | 1891-1897 |
 | Allison, William B. (IA) | 1897-1908 |
 | Hale, Eugene (ME) | 1908-1911 |
 | Cullom, Shelby (IL) | 1911-1913 |
 | Gallinger, Jacob H. (NH) | 1913-1918 |
 | Lodge, Henry Cabot, Sr. (MA) | 1918-1924 |
 | Curtis, Charles (KS) | 1924-19291 |
 | Watson, James E. (IN) | 1929-19332 |
 | McNary, Charles L. (OR) | 1933-19443 |
 | Vandenberg, Arthur H. (MI) | 1945-1946 |
 | Millikin, Eugene D. (CO) | 1947-1956 |
 | Saltonstall, Leverett (MA) | 1957-1966 |
 | Smith, Margaret Chase (ME) | 1967-1972 |
 | Cotton, Norris (NH) | 1973-1974 |
 | Curtis, Carl T. (NE) | 1975-1978 |
 | Packwood, Robert (OR) | 1979-1980 |
 | McClure, James A. (ID) | 1981-1984 |
 | Chafee, John (RI) | 1985-1990 |
 | Cochran, William Thad (MS) | 1991-1996 |
 | Mack, Connie (FL) | 1997-2001 |
 | Santorum, Richard J. (PA) | 2001-2007 |
 | Kyl, Jon (AZ) | 2007 |
 | Alexander, Lamar (TN) | 2008-2012 |
 | Thune, John (SD) | 2012-present |
1Republican senators elected Charles Curtis of Kansas as conference chairman on November 28, 1924, and as their first floor leader on March 5, 1925. Curtis, James Watson, and Charles McNary all served in dual roles as conference chairmen and party floor leaders. In 1945, the two positions were separated, with Arthur Vandenberg becoming conference chairman while Wallace H. White became Republican party floor leader. The positions have remained separated.
2Also served as Republican floor leader.
3Also served as Republican floor leader.
| Senator | Term | |
|---|---|---|
 | Stevenson, John W. (KY) | ended 1877 |
 | Wallace, William (PA) | 1878-1881 |
 | Pendleton, George (OH) | 1881-1885 |
 | Beck, James (KY) | 1885-1890 |
 | Gorman, Arthur P. (MD) | 1890-1898 |
 | Turpie, David (IN) | 1898-1899 |
 | Jones, James K. (AR) | 1899-1903 |
| Gorman, Arthur P. (MD) | 1903-1906 |
 | Blackburn, Joseph C. S. (KY) | 1906-1907 |
 | Culberson, Charles A. (TX) | 1907-1909 |
 | Money, Hernando D. (MS) | 1909-1911 |
 | Martin, Thomas S. (VA) | 1911-1913 |
 | Kern, John Worth (IN) | 1913-1917 |
| Martin, Thomas S. (VA) | 1917-1919 |
 | Underwood, Oscar W. (AL) | 1920-19231 |
 | Robinson, Joseph T. (AR) | 1923-1937 |
 | Barkley, Alben W. (KY) | 1937-1949 |
 | Lucas, Scott W. (IL) | 1949-1951 |
 | McFarland, Ernest W. (AZ) | 1951-1953 |
 | Johnson, Lyndon B. (TX) | 1953-1961 |
 | Mansfield, Mike (MT) | 1961-1977 |
 | Byrd, Robert C. (WV) | 1977-1989 |
 | Mitchell, George J. (ME) | 1989-1995 |
 | Daschle, Thomas A. (SD) | 1995-January 3, 2005 |
 | Reid, Harry M. (NV) | January 3, 2005-January 3, 2017 |
 | Schumer, Charles E. (NY) | January 3, 2017-present |
1Note: Beginning in 1920, the Democratic Conference chairperson also served as Democratic floor leader. In that year, Oscar Underwood became the first officially designated Democratic floor leader, and the tradition of combining the two positions continues to this day.
Sources for this information include: Gerald Gamm and Steven S. Smith, “Emergence of Senate Party Leadership,” in Bruce I, Oppenheimer, ed., U.S. Senate Exceptionalism (Ohio State University Press, 2002), pp. 212-238; “Rules of the Senate Republican Conference,” September 24, 1990; U.S. Congress, Senate, Majority and Minority Leaders of the Senate, by Floyd M. Riddick, S. Doc. 100-29, 100th Cong., 2d sess., 1988.
