The 2024 elections underscored the deepening partisan divide in American politics, with most states aligning their presidential and Senate votes. Yet, four states bucked the trend by reelecting or choosing Democratic senators while voting Republican in the presidential race, doubling the number of “mismatches” seen in recent years.
Arizona, Michigan, Nevada, and Wisconsin stood out as exceptions, electing Democrats to the Senate despite supporting Donald Trump in his successful bid for the presidency. This marks the highest number of such mismatches since 2018, when seven states saw split outcomes in Senate and presidential contests.
Fewer Split Outcomes Highlight National Trend
The four mismatches in 2024 represent nearly 12% of the 34 Senate races held this year, a notable increase compared to the nearly seamless alignment in Senate contests since 2016. Between 2012 and 2022, 91% of Senate races aligned with the state’s presidential vote, according to Pew Research Center data.
The recent uptick in mismatched outcomes remains far below historical levels. For instance, in the 1980s, mismatches were more common, with rates peaking at 59% in the 1986 elections. That year, Democrats won 20 of 34 Senate races in states carried by President Ronald Reagan two years earlier.
The 2024 Mismatches: Democratic Senate Wins in GOP States
The states where Democrats triumphed in Senate races despite Trump’s presidential win are:
- Arizona: Rep. Ruben Gallego secured a victory to replace independent Sen. Kyrsten Sinema.
- Michigan: Rep. Elissa Slotkin was elected to succeed retiring Sen. Debbie Stabenow.
- Nevada: Incumbent Sen. Jacky Rosen fended off challenger Sam Brown.
- Wisconsin: Incumbent Sen. Tammy Baldwin narrowly defeated financier Eric Hovde.
These results reflect a notable exception to the broader partisan alignment that has dominated Senate races over the past decade. No states in 2024 elected Republican senators while voting for Democratic presidential candidate Kamala Harris.
Historical Context: Partisan Sorting and Declining Split Votes
The decline in split-ticket voting for Senate and House races is part of a broader trend. The number of states with split Senate delegations – senators from different parties – has dropped to just three (Maine, Pennsylvania, and Wisconsin) in the incoming 119th Congress. This is the lowest level since the direct election of senators began in 1914.
Similarly, split-ticket voting in U.S. House races has dwindled, with fewer districts flipping between parties. In 2024, fewer than a dozen House seats changed party control, highlighting the entrenched partisan identities of most districts.
Polarization and Partisan Loyalty
Analysts attribute the decrease in mismatched outcomes to rising political polarization and partisan loyalty. Voters are increasingly likely to back candidates from the same party across the ballot, driven by heightened ideological divides and personal animosity between Democrats and Republicans.
As the incoming Congress takes shape, the deepening partisan alignment suggests continued challenges for bipartisanship and cross-party cooperation in Washington.
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