The question of the annexation of Texas, forced to the front in the interest of the slaveholding States, united the Democrats and elected James K. Polk President in 1844; while Clay and the Whig Party, who confidently expected success, lost the election by reason of the growth of the Antislavery or Liberty party which cast a large vote in New York,—­the pivotal State, without whose support in the Electoral College the carrying of the other Northern States went for nought.  The Mexican War followed; and in 1846 David Wilmot of Pennsylvania moved an amendment to a bill appropriating $2,000,000 for final negotiations, providing that in all territories acquired from Mexico slavery should be prohibited.  The Wilmot Proviso was lost, but arose during the next four years, again and again, in different forms, but always as the standard of the antislavery Northerners.

When the antislavery agitation had reached an alarming extent, and threatened to drive the South into secession from the Union, Clay appeared once again in his great role as a pacificator.  To preserve the Union was the dearest object of his public life.  He would by a timely concession avert the catastrophe which the Southern leaders threatened, and he probably warded off the inevitable combat when, in 1850, he made his great speech, in favor of sacrificing the Wilmot Proviso, and enacting a more stringent fugitive-slave law.

In 1848, embittered by having been set aside as the nominee of the Whig party for the presidency in favor of General Taylor, one of the successful military chieftains in the Mexican War,—­who as a Southern man, with no political principles or enemies, was thought to be more “available,”—­Clay had retired from the Senate, and for a year had remained at Ashland, nominally and avowedly “out of politics,” but intensely interested, and writing letters about the new slavery complications.  In December, 1849, he was returned to the Senate, and inevitably became again one of the foremost in all the debates.

When the conflict had grown hot and fierce, in January, 1850, Clay introduced a bill for harmonizing all interests.  As to the disputed question of slavery in the new territory, he would pacify the North by admitting California as a free State, and abolishing slavery and the slave-trade in the District of Columbia; while the South was to be placated by leaving Utah and New Mexico unrestricted as to slavery, and by a more efficient law for the pursuit and capture of fugitive slaves.  His speech occupied two days, delivered in great physical exhaustion, and was “an appeal to the North for concession and to the South for peace.”  Like Webster, who followed with his renowned “Seventh-of-March speech” and who alienated Massachusetts because he did not go far enough for freedom, Clay showed that there could be no peaceable secession, that secession meant war, and that it would be war to propagate a wrong, in which the sympathy of all mankind would be against us.