It's known that John Hinckley, Jr. trailed Carter in the months leading up to the election before switching targets to the newly-inaugurated Ronald Reagan, leading to the well-known assassination attempt in March 1981.
What if Hinckley took a chance at his original target and shot Carter? Would he have survived? Would it affect the election had he lived? Would Mondale have replaced him on the ticket had he died? Would Carter's image be rehabilitated? Would gun control become a campaign issue?