The correct answer to this open question is the following.
Southerners claimed that abolitionist victories were creating a "wedge" in the Union. What they meant by this was that people from the South -who heavily supported slavey in their territories- thought that as abolitionists' ideas spread to the northern states, these somehow weakened the Union in that these ideas confronted their people through so much debate. For the southerners, this represented an advantage and creation distraction while the South gained time and maintained slavery in the large plantations, producing the kinds of crops that moved their economy.
Were they correct? Not at all but they had a point in that so much debate on the issue of slavery and the increasing idea of abolitionism distracted decision-makers in the northern states. Those were the years were more supporters of abolition made their moves. For instance, in Rochester, New York, Frederick Douglass led the newspaper "The North Star," an abolitionist publication that somehow exerted pressure in the public opinion.
