### Split-Ticket Voting Sees a Notable Rise in 2024 Elections

As the dust settles on the 2024 election, an intriguing development has emerged: an increase in split-ticket outcomes between presidential and U.S. Senate races. Historically rare, split-ticket voting saw a considerable uptick this year, with at least three states—Michigan, Nevada, and Wisconsin—displaying different party preferences for president and Senate. Arizona is also expected to join this group, as Democratic Rep. Ruben Gallego leads with a narrow margin.

In contrast to previous presidential elections in 2016 and 2020, where only Maine in 2020 displayed a split-ticket outcome, the 2024 election has witnessed a surge. This year, 12% of the states with both presidential and Senate races on the ballot had split-ticket outcomes, the highest since 2012. However, it's important to note that in Pennsylvania, a straight-ticket Republican win seems likely with Dave McCormick holding a slim lead over Democratic Sen. Bob Casey Jr.

The correlation between margins for presidential and Senate races in states that voted appears to have a significant similarity. The correlation in 2024 was about 0.95, mirroring the high level of alignment seen in 2020, suggesting that while split-ticket outcomes have increased, they haven't necessarily resulted from a more substantial number of voters splitting their tickets between parties.

Interestingly, close races played a crucial role in producing split-ticket results. Four of the five closest Senate races, each decided by narrow margins, are poised to result in split-ticket outcomes favorable to Democrats. Factors contributing to these results may include incumbency status and candidate quality.

Notably, Arizona's situation is unique. Gallego has significantly outperformed Vice President Kamala Harris in raw vote count, while Republican Kari Lake has underperformed compared to Trump. This suggests a notable segment of Trump voters backed Gallego for Senate.

In other states like Nevada, Michigan, and Wisconsin, the phenomenon appeared different. For instance, in Nevada, Republican Sam Brown garnered nearly 10% fewer votes than Trump, indicating potential ballot roll-off or third-party voting rather than outright split-ticket voting. The margins were narrower in Michigan and Wisconsin, where GOP Senate candidates also lagged Trump's vote total by smaller percentages.

Overall, split-ticket outcomes have undeniably influenced the Senate race landscape in 2024. If Republicans had won every Senate race in states Trump carried, they would hold 57 seats instead of the likely 53. This election cycle illustrates that even with a rise in split-ticket outcomes, the alignment between presidential and Senate votes remains historically high, showing that only in the tightest races did split-ticket voters make a substantial impact.