A large number of distinguished Democrats in the North also entertained the strongest anti-slavery convictions, and were determined, at the risk of separating from their party associates, to resist the spread of slavery into free territory.

Among the most conspicuous of these were Salmon P.
Chase, John P.Hale, Hannibal Hamlin, Preston King, John M.Niles, David Wilmot, David K.Cartter, and John Wentworth.

They had many co-laborers and a band of determined and courageous followers.
They were especially strong in the State of New York, and, under the name of Barnburners, wrought changes which affected the political history of the entire country.
The two great parties on the eve of the Mexican war were thus somewhat similarly situated.

In the South all the members of both were, by the supposed necessity of their situation, upholders of slavery, though the Democrats were on this question more aggressive, more truculent, and more menacing, than the Whigs.

The Southern Whigs, under the lead of Mr.Clay, had been taught that slavery was an evil, to be removed in some practicable way at some distant period, but not to be interfered with, in the States where it existed, by outside influence or force.