Final answer:
The Missouri Compromise of 1820 supports Potter's view by highlighting how sectional compromises over slavery just delayed and foreshadowed the eventual Civil War.
Step-by-step explanation:
One historical event during the period of 1786-1861 that could be used to support David M. Potter's view in The Impending Crisis is the Missouri Compromise of 1820. This event was essential because it attempted to balance the power between slave and free states with the admission of Missouri as a slave state and Maine as a free state, and it established a geographic boundary for slavery in the western territories. The compromise reflected the intensifying sectional conflict and foreshadowed the intractability of the slavery issue by drawing a hard line between the North and South. This event is emblematic of the compromises that merely delayed the eventual sectional confrontation that Potter describes as leading to the cataclysm of the Civil War.