Although William McKinley ran an everyman, "morning in America" type campaign, the times he lived in were very dangerous.
It's astonishing to think that a middle aged person in McKinley's age could have remembered so many presidents being assassinated in their life time. If you think about it, an adult in McKinley's age could have been a child during the Civil War and remembered Lincoln being assassinated in 1865. They would have remembered Garfield being killed in 1881 as a young man or woman in their 20's or early 30's and then would witness McKinley being assassinated in 1901 as a person in their 40's or 50's.
If you read American history ahead a little bit, the same person would have witnessed the assassination attempt on Theodore Roosevelt in 1912 when he famously continued his speech and yelled, "It takes more than that to stop a Bull Moose" with a bullet in his chest that was prevented from killing him by a manuscript he had in his breast pocket.
This means that a person who was a young child when Lincoln was assassinated that lived to the age of 65 or 70, would have remembered 4 out of the 12 presidents during their lifetime either being killed or having attempts on their lives.
It's easy for the instability of this time period to be overshadowed by the twentieth century with its Great War, Second World War and 50 year Cold War where many Americans thought they were in imminent danger of nuclear annihilation. It's even easy for this period to be overshadowed by our current National Security State, but we shouldn't forget just how dangerous the times were that the Gilded Age and early twentieth century presidents lived in.