Partisan rancor over the Kansas-Nebraska Act of 1854 plunged Union politics into turmoil. The Republican Party rose out of the carnage. The party's key platform was an economic policy that benefited the North more than the South, but what truly aggravated the South was the party's aim to halt the expansion of slavery.

The Republican Party itself was torn over the course of the war, dividing itself into three distinct splinters. Conservative Republicans favored the gradual emancipation of slaves and kindness toward the South. Moderate Republicans urged faster emancipation and some punitive economic and political sanctions. Radical Republicans sought immediate emancipation and harsh punishment against the South.

In the Democratic Party, Peace Democrats considered the war unconstitutional and supported the Southern cause. Their position was that the Republican Party caused the Civil War by forcing the South to secede and did so only to strengthen its own power base and force racial equality, a phrase intended to frighten racists who might otherwise support the Union cause. War Democrats believed strongly in the Union cause and supported the Lincoln administration on most issues. Most War Democrats had no strong feelings regarding the institution of slavery in the South and felt no compunction about restoring the Union without emancipation if necessary.

Proslavery Voices in the Union

Slavery was not the most important issue at the very onset of hostilities; the real issue was Southern independence. The Confederacy was fighting for its very existence, while the North's biggest war aim was the preservation of the Union.

Indeed, the issue of slavery was not universally condemned in the North. A good share of Northerners didn't really care if the institution continued in the South or not, and many hoped that it would. In many cases, Northern advocacy for Southern slavery stemmed from fears that an influx of newly freed Southern blacks would flood the North, take jobs from whites, and drive down wages.

The issue of slavery forced Lincoln to walk a thin line as war became imminent. Though morally opposed to slavery himself, Lincoln needed the congressional support of Northern Democrats, most of whom had little objection to the continuation of slavery in the South, so both he and Congress went out of their way to stress that they wanted to preserve the Union without interfering with the unique institutions of any state. It was hoped that this tact would also help appease the slaveholding border states of Maryland, Kentucky, and Missouri, which wavered dangerously on which side to support.

Though he greatly opposed slavery, Lincoln's greatest concern as president was keeping the nation together at any cost, and he was willing to compromise greatly to do it. Only later in the conflict would the elimination of slavery in the South become a primary aim of the Union's war effort.