The positions of party floor leader are not included in the Constitution but developed gradually in the 20th century. The first floor leaders were formally designated in 1920 (Democrats) and 1925 (Republicans).

The Senate Republican and Democratic floor leaders are elected by the members of their party in the Senate at the beginning of each Congress. Depending on which party is in power, one serves as majority leader and the other as minority leader. The leaders serve as spokespersons for their parties' positions on issues. The majority leader schedules the daily legislative program and fashions the unanimous consent agreements that govern the time for debate.

The majority leader has the right to be called upon first if several senators are seeking recognition by the presiding officer, which enables him to offer motions or amendments before any other senator.

Elected at the beginning of each Congress by members of their respective party conferences to represent them on the Senate floor, the majority and minority leaders serve as spokesmen for their parties' positions on the issues. The majority leader has also come to speak for the Senate as an institution. Working with the committee chairs and ranking members, the majority leader schedules business on the floor by calling bills from the calendar and keeps members of his party advised about the daily legislative program. In consultation with the minority leader, the majority leader fashions unanimous consent agreements by which the Senate limits the amount of time for debate and divides that time between the parties. When time limits cannot be agreed on, the majority leader might file for cloture to shut off debate. Occupying the front desks on the center aisle, the two leaders coordinate party strategy and try to keep their parties united on roll-call votes.

The leaders spend much of their time on or near the Senate floor, to open the day's proceedings, keep legislation moving, and protect the rights and interests of party members. When several senators are seeking recognition at the same time, the presiding officer in the Senate will call on the majority leader first, then on the minority leader, and then on the managers of the bill being debated, in that order. This right of first recognition enables the majority leader to offer amendments, substitutes, and motions to reconsider before any other senator. Former Majority Leader Robert C. Byrd called first recognition "the most potent weapon in the Majority Leader's arsenal."

The posts of majority and minority leader are not included in the Constitution, as are the president of the Senate (the vice president of the United States) and the president pro tempore. Instead, party floor leadership evolved out of necessity. During the nineteenth century, floor leadership was exercised by the chair of the party conference and the chairs of the most powerful standing committees. In 1913, to help enact President Woodrow Wilson's ambitious legislative program, Democratic Conference chairman John Worth Kern of Indiana began functioning along the lines of the modern majority leader. In 1919, when Republicans returned to the majority, Republican Conference Chairman Henry Cabot Lodge, Sr. also acted as floor leader. Not until 1925 did Republicans officially designate Senator Charles Curtis of Kansas as majority leader, separate from the Conference chair. (Five years earlier, the Democrats had specifically named Oscar Underwood of Alabama as minority leader.)

Although party floor leadership posts carry great responsibility, they provide few specific powers. Instead, floor leaders have largely had to depend on their individual skill, intelligence, and personality. Majority leaders seek to balance the needs of senators of both parties to express their views fully on a bill with the pressures to move the bill as quickly as possible toward enactment. These conflicting demands have required majority leaders to develop skills in compromise, accommodation, and diplomacy. Lyndon Johnson, who held the post in the 1950s, once said that the greatest power of the majority leader was "the power of persuasion."

The majority leader usually works closely with the minority leader so that, as Senator Bob Dole explained, "we never surprise each other on the floor." The party leaders meet frequently with the president and with the leaders of the House of Representatives. The majority leader also greets foreign dignitaries visiting the Capitol.

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. These assistant leaders 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.   List of Party Whips

66th Congress (1919-1921)

Majority Leader: None.

Minority Leader: Oscar W. Underwood (D-AL)

Note: Oscar W. Underwood became the first elected party leader on April 27, 1920. There was no elected Republican floor leader prior to 1925. During the 66th Congress, Henry Cabot Lodge (R-MA) was the party conference chairman and served as an unofficial party leader.

--------------------------------------------------------------------------------

67th Congress (1921-1923)

Majority Leader: None.

Minority Leader: Oscar W. Underwood (D-AL)

Note: Henry Cabot Lodge (R-MA) continued to serve as unofficial Republican leader.

--------------------------------------------------------------------------------

68th Congress (1923-1925)

Majority Leader: Charles Curtis (R-KS)

Minority Leader: Joseph T. Robinson (D-AR)

Note: Henry Cabot Lodge (R-MA) died on November 9, 1924. Charles Curtis was elected Republican floor leader on March 5, 1925. The Democratic party elected Joseph T. Robinson as floor leader on December 3, 1923.

--------------------------------------------------------------------------------

69th Congress (1925-1927)

Majority Leader: Charles Curtis (R-KS)

Minority Leader: Joseph T. Robinson (D-AR)

--------------------------------------------------------------------------------

70th Congress (1927-1929)

Majority Leader: Charles Curtis (R-KS)

Minority Leader: Joseph T. Robinson (D-AR)

Note: Charles Curtis resigned his Senate seat on March 3, 1929, having been elected Vice President of the United States.

--------------------------------------------------------------------------------

71st Congress (1929-1931)

Majority Leader: James E. Watson (R-IN)

Minority Leader: Joseph T. Robinson (D-AR)

Note: James E. Watson was elected Republican leader on March 5, 1929.

--------------------------------------------------------------------------------

72nd Congress (1931-1933)

Majority Leader: James E. Watson (R-IN)

Minority Leader: Joseph T. Robinson (D-AR)

Note: James Watson lost his reelection bid in 1932 and left office on March 3, 1933.

--------------------------------------------------------------------------------

73rd Congress (1933-1935)

Majority Leader: Joseph T. Robinson (D-AR)

Minority Leader: Charles L. McNary (R-OR)

Note: Charles L. McNary was elected Republican leader on March 7, 1933.

--------------------------------------------------------------------------------

74th Congress (1935-1937)

Majority Leader: Joseph T. Robinson (D-AR)

Minority Leader: Charles L. McNary (R-OR)

--------------------------------------------------------------------------------

75th Congress (1937-1939)

Majority Leader: Joseph T. Robinson (D-AR); Alben Barkley (D-KY)

Minority Leader: Charles L. McNary (R-OR)

Note: Joseph T. Robinson died on July 14, 1937. Alben Barkley was elected Democratic leader on July 22, 1937.

--------------------------------------------------------------------------------

76th Congress (1939-1941)

Majority Leader: Alben Barkley (D-KY)

Minority Leader: Charles L. McNary (R-OR)

Note: In 1940, at the request of Senator McNary, Senator Warren R. Austin (R-VT) served as acting leader.

--------------------------------------------------------------------------------

77th Congress (1941-1943)

Majority Leader: Alben Barkley (D-KY)

Minority Leader: Charles L. McNary (R-OR)

--------------------------------------------------------------------------------

78th Congress (1943-1945)

Majority Leader: Alben Barkley (D-KY)

Minority Leader: Wallace H. White, Jr. (R-ME)

Note: Although Charles McNary continued to be officially listed as minority leader until his death on February 25, 1944, Wallace H. White, Jr. served as acting leader during McNary's illness and was elected Republican leader on January 4, 1945. He retired from the Senate on January 3, 1949.

--------------------------------------------------------------------------------

79th Congress (1945-1947)

Majority Leader: Alben Barkley (D-KY)

Minority Leader: Wallace H. White, Jr. (R-ME)

--------------------------------------------------------------------------------

80th Congress (1947-1949)

Majority Leader: Wallace H. White, Jr. (R-ME)

Minority Leader: Alben Barkley (D-KY)

Note: Alben Barkley resigned his Senate seat on January 19, 1949, having been elected Vice President of the United States.

--------------------------------------------------------------------------------

81st Congress (1949-1951)

Majority Leader: Scott W. Lucas (D-IL)

Minority Leader: Kenneth S. Wherry (R-NE)

Note: Scott W. Lucas was elected Democratic leader on December 31, 1948, to be in effect on January 20, 1949. Lucas lost his bid for reelection in 1950 and left office on January 3, 1951. Kenneth W. Wherry was elected Republican leader on January 3, 1949.

--------------------------------------------------------------------------------

82nd Congress (1951-1953)

Majority Leader: Ernest W. McFarland (D-AZ)

Minority Leader: Kenneth S. Wherry (R-NE); Styles Bridges (R-NH)

Note: Ernest W. McFarland was elected Democratic leader on January 2, 1951. He lost his bid for reelection in 1952, and left office on January 3, 1953. Kenneth Wherry died on November 29, 1951. Styles Bridges was elected Republican leader on January 8, 1952.  He chose not to continue as party leader in the 83rd Congress, instead becoming president pro tempore and chair of the Committee on Appropriations.  

--------------------------------------------------------------------------------

83rd Congress (1953-1955)

Majority Leader: Robert A. Taft (R-OH); William F. Knowland (R-CA)

Minority Leader: Lyndon B. Johnson (D-TX)

Note: Robert Taft was elected Republican leader on January 2, 1953. He died the following July 31. William Knowland was elected Republican leader on August 4, 1953. Lyndon Johnson was elected Democratic leader on January 2, 1953. William Knowland was the youngest majority leader in Senate history, being elected to the position at the age of 45. When Lyndon Johnson became majority leader two years later, he was 46 years old, ranking him second behind Knowland. Johnson was the youngest Democratic floor leader.

-------------------------------------------------------------------------------

84th Congress (1955-1957)

Majority Leader: Lyndon B. Johnson (D-TX)

Minority Leader: William F. Knowland (R-CA)

--------------------------------------------------------------------------------

85th Congress (1957-1959)

Majority Leader: Lyndon B. Johnson (D-TX)

Minority Leader: William F. Knowland (R-CA)

Note:  William Knowland retired from the Senate at the end of the 85th Congress.

--------------------------------------------------------------------------------

86th Congress (1959-1961)

Majority Leader: Lyndon B. Johnson (D-TX)

Minority Leader: Everett M. Dirksen (R-IL)

Note: Lyndon Johnson resigned his Senate seat on January 3, 1961, having been elected Vice President of the United States. Everett Dirksen was elected Republican leader on January 7, 1959.

--------------------------------------------------------------------------------

87th Congress (1961-1963)

Majority Leader: Mike Mansfield (D-MT)

Minority Leader: Everett M. Dirksen (R-IL)

Note: Mike Mansfield was elected Democratic leader on January 3, 1961, and served until January 3, 1977, making him the longest-serving majority leader in Senate history.

--------------------------------------------------------------------------------

88th Congress (1963-1965)

Majority Leader: Mike Mansfield (D-MT)

Minority Leader: Everett M. Dirksen (R-IL)

--------------------------------------------------------------------------------

89th Congress (1965-1967)

Majority Leader: Mike Mansfield (D-MT)

Minority Leader: Everett M. Dirksen (R-IL)

--------------------------------------------------------------------------------

90th Congress (1967-1969)

Majority Leader: Mike Mansfield (D-MT)

Minority Leader: Everett M. Dirksen (R-IL)

--------------------------------------------------------------------------------

91st Congress (1969-1971)

Majority Leader: Mike Mansfield (D-MT)

Minority Leader: Everett M. Dirksen (R-IL); Hugh D. Scott, Jr. (R-PA)

Note: Everett Dirksen died on September 7, 1969. Hugh Scott was elected Republican leader on September 24, 1969.

--------------------------------------------------------------------------------

92nd Congress (1971-1973)

Majority Leader: Mike Mansfield (D-MT)

Minority Leader: Hugh D. Scott, Jr. (R-PA)

--------------------------------------------------------------------------------

93rd Congress (1973-1975)

Majority Leader: Mike Mansfield (D-MT)

Minority Leader: Hugh D. Scott, Jr. (R-PA)

--------------------------------------------------------------------------------

94th Congress (1975-1977)

Majority Leader: Mike Mansfield (D-MT)

Minority Leader: Hugh D. Scott, Jr. (R-PA)

Note: Mike Mansfield and Hugh Scott both retired from the Senate at the end of the 94th Congress.

--------------------------------------------------------------------------------

95th Congress (1977-1979)

Majority Leader: Robert C. Byrd (D-WV)

Minority Leader: Howard H. Baker, Jr. (R-TN)

Note: Robert C. Byrd was elected Democratic leader on January 4, 1977. Howard H. Baker, Jr., was elected Republican leader on January 4, 1977.

--------------------------------------------------------------------------------

96th Congress (1979-1981)

Majority Leader: Robert C. Byrd (D-WV)

Minority Leader: Howard H. Baker, Jr. (R-TN)

--------------------------------------------------------------------------------

97th Congress (1981-1983)

Majority Leader: Howard H. Baker, Jr. (R-TN)

Minority Leader: Robert C. Byrd (D-WV)

--------------------------------------------------------------------------------

98th Congress (1983-1985)

Majority Leader: Howard H. Baker, Jr. (R-TN)

Minority Leader: Robert C. Byrd (D-WV)

Note: Howard Baker retired from the Senate at the end of the 98th Congress.

--------------------------------------------------------------------------------

99th Congress (1985-1987)

Majority Leader: Robert Dole (R-KS)

Minority Leader: Robert C. Byrd (D-WV)

Note: Robert Dole was elected Republican leader on November 28, 1984, effective January 3, 1985.

--------------------------------------------------------------------------------

100th Congress (1987-1989)

Majority Leader: Robert C. Byrd (D-WV)

Minority Leader: Robert Dole (R-KS)

Note:  Robert Byrd resigned as majority leader to become chair of the Senate Committee on Appropriations in the 101st Congress and was elected president pro tempore on January 3, 1989.

--------------------------------------------------------------------------------

101st Congress (1989-1991)

Majority Leader: George J. Mitchell (D-ME)

Minority Leader: Robert Dole (R-KS)

Note: George Mitchell was elected Democratic leader on November 29, 1988, effective January 3, 1989.

--------------------------------------------------------------------------------

102nd Congress (1991-1993)

Majority Leader: George J. Mitchell (D-ME)

Minority Leader: Robert Dole (R-KS)

--------------------------------------------------------------------------------

103rd Congress (1993-1995)

Majority Leader: George J. Mitchell (D-ME)

Minority Leader: Robert Dole (R-KS)

Note: George Mitchell retired from the Senate at the end of the 103rd Congress.

--------------------------------------------------------------------------------

104th Congress (1995-1997)

Majority Leader: Robert Dole (R-KS); Trent Lott (R-MS)

Minority Leader: Thomas A. Daschle (D-SD)

Note: On December 22, 1995, Senator Robert Dole broke Charles McNary's record as longest-serving Republican leader, having served since January 3, 1985, ten years, eleven months, and nine days. Dole resigned from the Senate on June 11, 1996, to devote time to his presidential campaign. Trent Lott was elected Republican leader on June 12, 1996. Thomas Daschle was elected Democratic leader on December 2, 1994.

--------------------------------------------------------------------------------

105th Congress (1997-1999)

Majority Leader: Trent Lott (R-MS)

Minority Leader: Thomas A. Daschle (D-SD)

--------------------------------------------------------------------------------

106th Congress (1999-2001)

Majority Leader: Trent Lott (R-MS)

Minority Leader: Thomas A. Daschle (D-SD)

-------------------------------------------------------------------------------

107th Congress (2001-2003)

Majority Leader: Thomas A. Daschle (D-SD)

Minority Leader:  Trent Lott (R-MS)

Note:  From January 3 to January 20, 2001, with the Senate divided evenly between the two parties, the Democrats held the majority due to the deciding vote of outgoing Democratic Vice President Al Gore. Senator Thomas A. Daschle served as majority leader at that time. Beginning on January 20, 2001, Republican Vice President Richard Cheney held the deciding vote, giving the majority to the Republicans. Senator Trent Lott resumed his position as majority leader on that date. On May 24, 2001, Senator James Jeffords of Vermont announced his switch from Republican to Independent status, effective June 6, 2001. He announced that he would caucus with the Democrats, giving that party a one-seat advantage and  changing control of the Senate back to the Democrats. Thomas A. Daschle again became majority leader on June 6, 2001. Trent Lott announced on December 20, 2002, that he would not continue as Republican leader in the 108th Congress. William Frist was elected Republican leader on Dec. 23, 2002, and began service on January 7, 2003.

--------------------------------------------------------------------------------

108th Congress (2003-2005)

Majority Leader: William H. Frist (R-TN)  

Minority Leader:  Thomas A. Daschle (D-SD)  

Note: Senator Thomas Daschle lost his reelection bid on November 2, 2004, and retired from the Senate on January 3, 2005. Democratic Whip Harry M. Reid was elected to the post for the 109th Congress.

--------------------------------------------------------------------------------

109th Congress (2005-2007)

Majority Leader: William H. Frist (R-TN)  

Minority Leader:  Harry M. Reid (D-NV)  

Note:  Senator William Frist retired from the Senate on January 3, 2007. Republican Whip Mitch McConnell was elected to the post of Republican Leader on November 15, 2006, for the 110th Congress.  

--------------------------------------------------------------------------------

110th Congress (2007-2009)

Majority Leader: Harry M. Reid (D-NV)  

Minority Leader:  Mitch McConnell (R-KY)

-------------------------------------------------------------------------------

111th Congress (2009-2011)

Majority Leader: Harry M. Reid (D-NV)

Minority Leader: Mitch McConnell (R-KY)

(those serving as party leader for six years or longer)

Mike Mansfield (D-MT) – 16 years
                Senate Service: 1953-1977
                Party Leader: 1961-1977
                Majority Leader: 1961-1977
                Minority Leader:  None.

Joseph T. Robinson (D-AR) – 14 years
                Senate Service:  1913-1937
                Party Leader:  1923-1937
                Majority Leader: 1933-1937
                Minority Leader:  1923-1933

Robert C. Byrd (D-WV) – 12 years
                Senate Service:  1959-present
                Party Leader:  1977-1989
                Majority Leader: 1977-1981; 1987-1989
                Minority Leader:  1981-1987

Alben Barkley (D-KY) – 12 years
                Senate Service: 1927-1949; 1955-1956
                Party Leader: 1937-1949
                Majority Leader: 1937-1947
                Minority Leader: 1947-1949

Robert Dole (R-KS) –11 years     
                Senate Service: 1969-1996
                Party Leader:  1985-1996
                Majority Leader:  1985-1987; 1995-1996
                Minority Leader: 1987-1995

Charles McNary (R-OR) – 11 years
                Senate Service:  1917-1944
                Party Leader:  1933-1944
                Majority Leader:  None.
                Minority Leader:  1933-1944

Everett M. Dirksen (R-IL) – 10 years        
                Senate Service:  1951-1969
                Party Leader:  1959-1969
                Majority Leader:  None.
                Minority Leader:  1959-1969

Thomas Daschle (D-SD) – 10 years           
                Senate Service: 1987-2005
                Party Leader:  1995-2005
                Majority Leader:  2001-2003
                Minority Leader: 1995-2001; 2003-2005

Howard Baker (R-TN) – 8 years
                Senate Service:  1967-1985
                Party Leader:  1977-1985
                Majority Leader:  1981-1985
                Minority Leader:  1977-1981

Lyndon B. Johnson (D-TX) – 8 years
                Senate Service: 1949-1961
                Party Leader: 1953-1961
                Majority Leader: 1955-1961
                Minority Leader:  1953-1955

Hugh Scott, Jr. (R-PA) – 8 years
                Senate Service: 1959-1977
                Party Leader: 1969-1977
                Majority Leader:  None.
                Minority Leader:  1969-1977

Trent Lott (R-MS) – 6.5 years
                Senate Service:  1989-2007
                Party Leader:  1996-2003
                Majority Leader:  1996-2001
                Minority Leader:  2001-2003

William F. Knowland (R-CA) – 6 years
                Senate Service:  1945-1959
                Party Leader:  1953-1959
                Majority Leader:  1953-1955
                Minority Leader:  1955-1959

George J. Mitchell (D-ME) – 6 years
                Senate Service: 1980-1995
                Party Leader: 1989-1995
                Majority Leader: 1989-1995
                Minority Leader:  None.

--------------------------------------------------------------------------------
Sources:

U.S. Congress.  Senate.  Majority and Minority Leaders of the Senate, by Floyd M. Riddick, S. Doc 100-29, 100th Congress, 2d session, 1988.

Byrd, Robert C. The Senate, 1789-1989: Addresses on the History of the United States Senate. Volume II (Washington: U.S. GPO, 1991).

Baker, Richard A. and Roger H. Davidson, eds.  First Among Equals: Outstanding Senate Leaders of the Twentieth Century (Washington, DC: Congressional Quarterly, 1991).

U.S. Congress. Senate. Minutes of the Senate Republican Conference: Sixty-second Congress through Eighty-eighth Congress, 1911-1964, edited by Wendy Wolff and Donald A. Ritchie. Washington: GPO, 1999, Senate Document 105-19.

U.S. Congress. Senate. Minutes of the Senate Democratic Conference: Fifty-eighth through Eighty-eighth Congresses, 1903-1964, edited by Donald A. Ritchie. Washington, GPO, 1999. Senate Document 105-20.

Biographical Directory of the U.S. Congress

--------------------------------------------------------------------------------