Strangely, every American president to have died in office was elected in a year divisible by 20:
William Henry Harrison (elected 1840, died in 1841, a month after taking office)
Abraham Lincoln (elected 1860, assassinated 1865)
James Garfield (elected 1880, assassinated 1881)
William McKinley (re-elected 1900, assassinated 1901)
Warren Harding (elected 1920, died of cerebral hemorrhage 1923)
FDR (re-elected 1940, died of a stroke 1945)
JFK (elected 1960, assassinated 1963)
There was an unsuccessful assassination attempt on Ronald Reagan (elected 1980).