Democrats counter-crusaded by warning that a Republican victory would bring a civil war.

The Republican platform opposed the repeal of the Missouri Compromise through the Kansas–Nebraska Act, which enacted the policy of popular sovereignty, allowing settlers to decide whether a new state would enter the Union as free or slave.

In sum, the campaign's true focus was against the system of slavery, which they felt was destroying the Republican values that the Union had been founded upon.

The Democrats also supported the plan to annex Cuba, advocated in the Ostend Manifesto, which Buchanan helped devise while serving as minister to Britain.

The most influential aspect of the Democratic campaign was a warning that a Republican victory would lead to the secession of numerous southern states.