These factors included the collapse of the nativist American Party, sectional strife in the Democratic Party, Northern voter dissatisfaction with the Supreme Court's March 1857 Dred Scott decision, political exposure of Democrats to chaotic violence in Kansas amid repeated attempts to impose slavery against the express will of a majority of its settlers, and a sharp decline in President Buchanan's popularity due to his perceived fecklessness.

The pivotal Dred Scott decision was only the second time the Supreme Court had overturned an Act of Congress on Constitutional grounds, after Marbury v. Madison.

Short of a majority, Republicans controlled the House with limited cooperation from smaller parties also opposing the Democrats.

Though not yet abolitionist, Republicans openly derived a primary partisan purpose from hostility to slavery while furnishing a mainstream platform for abolitionism.

Eight Northern anti-Lecompton Democrats favored a ban on slavery in Kansas, effectively upholding the Missouri Compromise their party had destroyed several years earlier.

A damaging public perception also existed that President Buchanan had improperly influenced and endorsed the Dred Scott decision, incorrectly believing that it had solved his main political problem.

The wide gap between Democratic rhetoric and results alienated voters, while defeat in the North and intra-party defection combined to make the party both more Southern and more radical.

Democrats lost seats in some slave states as the disturbing turn of national events and surge in sectional tensions alarmed a significant minority of Southern voters.