What made possible this remarkable eclipse of Know Nothings and surge of Republicans to become the North’s majority party within less than two years? Part of the answer lay in a dramatic decline of immigration, which during the years after 1854 fell to less than half of the level it had attained in the first half of the decade. But the main reason could be expressed in two words: Bleeding Kansas. Events in that far-off territory convinced most northerners that the slave power was after all a much greater threat to republican liberty than the Pope was.
