Lincoln rode on the growing popularity of the Republican Party and the divisions in the Democratic Party by pro and anti-slavery actors.

Several aspects of the Republican Party platform appealed to Northern voters. First, the party took a firm position against the expansion of slavery into the territories of the West. While many—perhaps even most—Northerners would not have favored emancipation of the South's millions of enslaved people, the institution was becoming more unpopular in the North with every passing year. Many Northerners came to believe with justification that a "slave power" conspiracy was dominating national politics, and the Republicans were popular because they resisted the expansion of slavery, the key policy demand of Southern congressmen. Republicans argued that the "normal condition of all the territory of the United States is that of freedom," a position that resonated not just with anti-slavery voters, but also with white men who feared their economic prospects were threatened by slavery. This was a crucial aspect of what was known as "free labor" ideology, which was the foundation of the Republican platform in 1860.

While slavery was the crucial issue in the election of 1860, the Republicans also favored other policies that appealed to many Northern voters. The Republicans advocated higher tariffs and a robust plan for internal improvements that included federal support for a transcontinental railroad, which they described as "imperatively demanded by the interests of the whole country." These measures were popular with powerful business interests in the North, but were generally opposed—especially the tariff—in the South. Ironically, Southern states made many of these business policies, long hamstrung by their opposition, possible with secession.