119th Congress Smashes Record Low for Number of Split US Senate Delegations

The number of states with U.S. Senators affiliated with different political parties has dropped from 19 to four in just seven congresses

A Smart Politics report published earlier this summer warned how the outputs of the partisan divide in this country were poised to get even more pronounced with the 2024 U.S. Senate elections.

A frequent refrain heard in Washington, D.C. is that members on opposite sides of the aisle no longer talk to each other, and members are therefore less personally invested in striking deals with the other side as well as moderating their tone and ultimately their policy positions.

Compounding the problem is the trend of fewer and fewer states represented by more than one party in the nation’s upper legislative chamber – thus providing fewer opportunities for members to build bipartisan bridges even within a state delegation.

Once the 119th Congress is seated on January 3rd of next year, only four states will be represented by U.S. Senators who do not share the same party affiliation: Maine, Pennsylvania, Vermont, and Wisconsin.

That marks the lowest number of split delegation states in the history of the direct election era.

[It should be noted that one these states – Vermont – still has a unified caucus with independent Bernie Sanders joining his fellow Democratic delegation member Peter Welch].

The 2024 cycle nearly sliced in half what was a previous record low in the chamber of seven states with split delegations heading into the November elections.

Republican pick-ups in Ohio, Montana, and West Virginia created all-GOP delegations in those three states and a Democratic open seat win for independent Kyrsten Sinema’s seat created a homogeneous state delegation in Arizona.

Pennsylvania create the only newly minted split delegation after Republican Dave McCormick’s narrow victory over Democratic incumbent Bob Casey.

The decimation of split U.S. Senate delegations has been swift over the last decade and is now nearly complete.

The 112th Congress convened in 2011 with 19 split delegation states representing all four regions of the country: eight in the Midwest (Illinois, Iowa, Missouri, Nebraska, North Dakota, Ohio, South Dakota, Wisconsin), five in the Northeast (Connecticut, Massachusetts, New Hampshire, Pennsylvania, Vermont), four in the South (Arkansas, Florida, Louisiana, North Carolina), and two in the West (Alaska, Nevada).

That number slid to 18 states at the beginning of the 113th Congress, 15 states for the 114th, 13 states for the 115th, 10 states for the 116th, and seven states for the 117th and 118th Congresses.

Prior to the 117th Congress, only one convened with fewer than 10 split-delegation states during the direct election era – the 84th Congress following the Election of 1954. That cycle produced nine states with one Democratic and Republican U.S. Senator in Arizona, Delaware, Illinois, Massachusetts, Michigan, Minnesota, Nevada, New York, and Wyoming.

From the 64th through the 118th Congresses (1915-2025), there have been an average of 16.2 states with split U.S. Senate delegations, with a peak of 27 states during the 96th Congress following the Election of 1978.

There were at least 20 states in the chamber with split delegations uninterrupted for a quarter-century stretch from 1969 through 1994.

Looking ahead to 2026, the number of split delegations will not decline for at least one cycle – presuming there are no resignations or deaths. There are no U.S. Senate elections on the ballot in Pennsylvania, Vermont, and Wisconsin in two years and it is extremely unlikely that Republican Susan Collins will lose her seat to an independent in the state.

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