Well we know that John Brown’s ultimate aim was to provoke a slave rebellion in the south and to try and bring about the destruction of chattel slavery in the United States. If we are supposing he escapes Harpers Ferry, then does that mean we are supposing it was a success? Or does he flee out the back door with no weapons and his crew slaughtered or captured? The second option seems out of character for Brown considering his composure in his trial and execution indicates he was perfectly willing to give his life once it became clear that the plan had failed. So that means his band escapes with the weapons then? Very few enslaved people rise up to join him because.. that was a pipe dream anyway.. but now the southern aristocracy is howling for his blood. He is the most wanted man in America and his band is now hiding somewhere in the Blue Ridge mountains for the winter. If you’re in this position, why kill the president? That doesn’t really further your plan in any way and for how notorious you are it would be extremely difficult to do. Not to mention that if Brown could suffer through Buchanan’s kowtowing to the slave power, I imagine he could survive a Douglas presidency without his blood lust being targeted at the president.
My point being that I’m not sure that Brown is your man for this. Contrary to popular myth, he wasn’t insane and he did have a plan (even if it was flawed). It’s possible that a disaffected radical abolitionist would do this, but it seems out of character for Brown. That being said, an abolitionist murdering the president would give a lot of ammunition to southerners. I could see the government trying to clamp down on New England abolitionism, but I’m not sure it would ultimately change trajectory against the broad free soil ideology. Men like Lincoln certainly wouldn’t tainted. They may have sought the end of chattel slavery, but the manner in which they pursued it wouldn’t associate them with men like the assassin. But I doubt the planters would see it that way. To them, it would be just another example of savage northern barbarians chomping at the bit to destroy the southern way of life. Fire eaters could easily spin it as a sign of the rottenness of the Federal system and propound immediate secession. If it’s the year after a semi-successful raid on Harper’s Ferry, then the tension in the US would be at boiling point. I could easily envision secession over this.
