As far back as 1850 it was clear that a new party, based on the anti-slavery sentiment that had been created by twenty years of agitation, was inevitable. Mr. Rhodes, speaking of conditions then, says: "It was, moreover, obvious to an astute politician like Seward, and probably to others, that a dissolution of parties was imminent; that to oppose the extension of slavery, the different anti-slavery elements must be organized as a whole; it might be called Whig or some other name, but it would be based on the principle of the Wilmot proviso"[56]—the meaning of which was, no more slave States.

Between 1850 and the passage of the Kansas-Nebraska act in 1854, new impulse had been given anti-slavery sentiment by fierce assaults on the new fugitive slave law and, as has been seen, by "Uncle Tom's Cabin." The Kansas-Nebraska act did serve as a cry for the rallying of all anti-slavery voters. That was all. It was a drum-call, in answer to which soldiers already enlisted fell into ranks, under a new banner. Any other drum-call—the application of another slave State for admission into the Union—would have served quite as well. Thus the Republican party came into existence in 1854. Mr. Rhodes sums up the reason for the existence of the new party and what it subsequently accomplished in the following pregnant sentence, "The moral agitation had accomplished its work, the cause (of anti-slavery) ... was to be consigned to a political party that brought to a successful conclusion the movement begun by the moral sentiment of the community,"[57]—which successful conclusion was, of course, the freeing of the slaves by a successful war.

For a time the new Republican party had a powerful competitor in another new organization. This was the American or Know-Nothing party. This other aspirant for power made an honest effort to revitalize the old Whig party under a new name and, by gathering in all the conservatives North and South, to put an end to sectionalism. Its signal failure conveys an instructive lesson. After many and wide-spread rumors of its coming, the birth of the American party was formally announced in 1854. It had been organized in secret and was bound together with oaths and passwords; its members delighted to mystify inquirers by refusing to answer questions, and soon they got the name of "Know-Nothings." The party had grown out of the "Order of the Star Spangled Banner," organized in 1850 to oppose the spread of Catholicism and indiscriminate immigration—the two dangers that were said to threaten American institutions.

The American party made its appeal: For the Union and against sectionalism; for Protestantism, the faith of the Fathers, against Catholicism that was being imported by foreigners; its shibboleth was "America for the Americans."

The Americans or Know-Nothings everywhere put out in 1854 full tickets and showed at once surprising strength. In the fall elections of that year they polled over one-fourth of all the votes in New York, two-fifths in Pennsylvania, and over two-thirds in Massachusetts, where they made a clean sweep of the State and Federal offices.[58]

They struck directly at sectionalism by exacting of their adherents the following oath:

"You do further swear that you will not vote for any one ... whom you know or believe to be in favor of a dissolution of the Union ... or who is endeavoring to produce that result."

The effect of this oath at the South was almost magical. The Whig party there was speedily absorbed by the Americans, and Southern Democrats by thousands joined the new party that promised to save the Union.[59] But the attitude of the Northern and Southern members of the American party soon became fundamentally different. Southerners saw their Northern allies in Vermont, Maine, and Massachusetts passing "personal liberty" laws.[60]

The Know-Nothings were strong enough in the elections of 1855 to directly check the progress of the new Republican party; but the American party, though it succeeded in electing a Speaker of the national House of Representatives in February, 1856, soon afterward went down to defeat. Even though led by such patriots as John Bell, of Tennessee, and Edward Everett, of Massachusetts, it could not stand against the storm of passion that had been aroused by the crusade against slavery.

There was a fierce and protracted struggle between the pro-slavery and anti-slavery men in Kansas for possession of the territorial government. Rival constitutions were submitted to Congress, and the debates over these were extremely bitter. In their excitement the Democrats again delighted their adversaries by committing what now seems to have been another blunder. They advocated the admission of Kansas under the "Lecompton Constitution." A review of the conflicting evidence appears to show that the Southerners were fairly outnumbered in Kansas and that the Lecompton Constitution did not express the will of the people.[61]