Trace the destruction of the national party system and the development of a regional party system between 1850 and 1860.

The destruction of the national two-party system after 1850 was a major political factor in bringing about secession and civil war. In 1850, the two-party system—Democrats and Whigs—was already under threat as Southerners within each party supported a number of issues related to the spread of slavery that Northerners found unacceptable.
The admission of California in 1850 as a free state was part of a compromise that eventually proved untenable. The Fugitive Slave Act, passed as part of the same compromise, was particularly noxious to Northerners, and Southerners grew increasingly annoyed as the North widely refused to obey it.
Northern Whigs had been especially opposed to the expansion of slavery into the territories, to the point where they nearly tore the party apart in the presidential election of 1852. By that time many Whigs, both Northern and Southern, had quit the party. In 1854, Northern Whigs found a home in the newly formed Republican Party, whose platform was to resist the expansion of slavery.
In the next few years, some former Whigs (a few of whom were Southerners) joined the Know-Nothing Party, a nativist party that formed in response to the massive waves of Irish immigrants. The Republicans had themselves formed in reaction to the Kansas–Nebraska Act, which opened the territories of Kansas and Nebraska to settlement and left the question of slavery's expansion there up to the settlers themselves, a policy known as "popular sovereignty." Popular sovereignty became the position of most Northern Democrats, with many Southern Democrats viewing the policy as insufficient to protect their interests. In effect, the Democratic Party was actually two parties, representing two different sets of regional interests.
Over time, bloodshed in Kansas over the issue of slavery caused even more Northerners to join the Republicans, and in 1860, that party nominated Abraham Lincoln, a former Whig congressman, for president. In that same year, Northern Democrats nominated Stephen Douglass, the architect of the Kansas–Nebraska Act, and Southern hard-liners bolted from the convention and nominated John Breckinridge. The Democratic Party had split, and Abraham Lincoln, who did not even appear on some ballots in the South, won the election. With a Republican in the White House, and having alienated themselves from the Democratic Party, Southern state seceded from the Union in 1860. Thus, in less than ten years, the national two-party system in the United States had fallen apart over the issue of slavery.