Split Senate delegations have become less common since the 1970s U.S. Senate delegations, by party composition Both Rep 14 15 15 12 12 11 11 17 18 18 18 19 21 17 14 15 14 20 19 Split 18 21 21 22 21 24 27
Before Jones’ win in December, only 13 states had split Senate delegations in the current Congress. That was the fewest in the past five decades, according to a Pew Research Center analysis of Senate membership data going back to the 90th Congress (1967-68). Now, with 14 split delegations, the current Senate is tied with several other Congresses for second-fewest in the past 50 years – there were 14 during most of the 107th Congress and all of the 108th and 109th Congresses, spanning 2001 through early 2007.
But politically divided delegations became more common in the 1960s and ’70s as decades-old patterns of state-level party dominance began to break down. By the 96th Congress of 1979-80, more than half the states (27) had split delegations, and from 1969 through 1994 more than 20 states sent split delegations to the Senate. Since then, despite some ups and downs, the trend has been toward more single-party delegations. As of now, 19 states have two Republican senators and 17 have two Democrats.
Split Senate delegations have become less common since the 1970s  | U.S. Senate delegations, by party composition  | Both Rep  | 11 12 10  | 14 15 15 12 12 11 11 17 18 18 18 19 21 17 14 15 14 20 19  | Split 18 21 21 22 21 24 27  | 25 24 23 21 21 22 21 19 19 19 14 14 14 17 15 19 18 15 14  | Both Dem 23 18 18 20 19 16  | 15 16 20 16 18 15 17  | 18 14 13 13 18  | 90th  | 95th  | 100th  | 105th  | 110th  | 115th  | (1967-68)  | (1977-78)  | (1987 -88)  | (1997-98)  | (2007-08)  | (2017-18)  | Note: Congress For the 90th-114th Congresses counts reflect party composition at the start of the first session. Counts for the 115th  | Congress include Sen. Doug Congresses Jones, D-Ala. Inde pendents are sitting counted separately even when they caucused with a major party,  | Due to disputed elections New Hampshire had only one sitting sena tor for the first seven months of the 94th Congress, and  | Minnesota had only one sitting sena tor for the first six months of the 111th Congress.  | Source: U.S Senate; Biographical Directory of the United States Congress; Pew Congress. Research Center ana lysis  | PEW RESEARCH CENTER 