Seward was elected to the U.S. Senate in 1849. Reelected in 1855, he was one of the Senate's most prominent members in the troubled years preceding the Civil War. A genial, gregarious man with intellectual interests, he was generally well liked, even by his political opponents.
Seward was an uncompromising foe of slavery, and, although he apparently tempered his public expressions so as not to alienate votes, he nevertheless made two remarks that became catchphrases of the antislavery forces. Voicing his opposition to the Compromise of 1850 in the Senate, he said (Mar. 11, 1850), "there is a higher law than the Constitution which regulates our authority over the domain." In a speech at Rochester on Oct. 25, 1858, he declared that there would exist "an irrepressible conflict" until the United States became either all slave or all free.
With the disintegration of the Whig party, Seward and Weed joined (1855) the new Republican party. Prominent as he was, Seward, despite (or possibly because of) the efforts of Weed's machine, was never able to secure the Republican presidential nomination. His friendship toward immigrants, especially the Irish, alienated members of the former Know-Nothing movement within the Republican party.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.