Final answer:
The key event leading into the Civil War that is discussed by Lincoln and Douglas is John Brown's raid on Harper's Ferry.
Step-by-step explanation:
The key event leading into the Civil War that is discussed by Lincoln and Douglas is John Brown's raid on Harper's Ferry.
John Brown's raid on Harper's Ferry was an unsuccessful attempt by abolitionist John Brown and his followers to incite a slave rebellion in the South. The raid took place in 1859 and was a significant event that further deepened the national division over slavery.