Slavery not only oppressed the Black slaves, it also ensured the subordination of the poor whites, Douglass argued:
The slaveholders... by encouraging the enmity of the poor, laboring white man against the Blacks, succeeds in making the said white man almost as much a slave as the Black slave himself... Both are plundered, and by the same plunderers. The slave is robbed, by his master, of all his earnings, above what is required for his physical necessities; and the white man is robbed by the slave system, of the just results of his labor, because he is flung into competition with a class of laborers who work without wages... At present, the slaveholders blind them to this competition, by keeping alive their prejudice against the slaves, as men-not against them as slaves. They appeal to their pride, often denouncing emancipation, as tending to place the white working man, on an equality with Negroes, and, by this means, they succeed in drawing off the minds of the poor whites from the real fact, that, by the rich slave-master, they are already regarded as but a single remove from equality with the slave.What Douglass describes in the South was mirrored in the North among white workers. While slavery flourished in the South, the Northern economy was entering a period of rapid expansion. The emerging labor movement of the 1830s was blunted by nativism and racism. The bulk of "native" workers reacted violently to the mass migrations of Irish workers in the 1840s and 1850s. Historian Mike Davis described the reaction of native-born workers to the Irish immigrants: "[The Irish] were met by the universal hostility of a native working class which rioted against them, evicted them from workplaces, refused them admission into trade unions, and tried to exclude them from the franchise."
Both native and immigrant labor competed for jobs, and accepted the argument that the emancipation of slaves would "flood" the labor market with four million Blacks. Free Blacks in the North (who numbered 250,000) were excluded from all the existing trade union. The question of slavery was thus also crucial to the working class in the North. Marx put it succinctly: "In the United States of America, every independent workers' movement was paralyzed as long as slavery disfigured a part of the republic. Labor in a white skin cannot emancipate itself where it is branded in a black skin."
plus ça change, plus c'est la même chose