Federal Slavery Legislation and Voting in U.S. Gubernatorial Elections, 1840–1860

The demise of the Whig Party in the 1850s has long been a subject of great attention among scholars and the general public. However, this historical development has received less attention from the vantage point of quantitative empirical analysis. Using state-level gubernatorial electoral returns from 1840 to 1860, we assess how major events like the passage of the Fugitive Slave Act/Compromise of 1850, the passage of the Kansas–Nebraska Act, and the rise of the Know Nothing Party influenced the transformation of America’s party system in the lead up to the Civil War. We find evidence linking the passage of the Kansas–Nebraska Act to a drop in support for Northern Whigs, Free Soilers, and (more suggestively) Northern Democrats. The results are consistent with a narrative of the Kansas–Nebraska Act unleashing fears among Free Soilers, ultimately leading to a coalescing around the new Republican Party.