Oh, and here's some maths I did next door that I thought I'd share:
Never. He's still alive
As for other presidents dying in office, it's happened EIGHT TIMES. In fact, we are currently at the longest run without a president dying in office since the early 1800s.
William Henry Harrison, Zachary Taylor, Abraham Lincoln, James A. Garfield, William McKinley, Warren G. Harding, Franklin D. Roosevelt and John F. Kennedy all died in office.
The Following VPs became Presidents:
* John Tyler - death of William Henry Harrison
* Millard Fillmore - death of Zachary Taylor
* Andrew Johnson - assassination of Abraham Lincoln
* Chester Arthur - assassination of James Garfield
* Theodore Roosevelt - assassination of William McKinley
* Calvin Coolidge - death of Warren Harding
* Harry Truman - death of Franklin Roosevelt
* Lyndon Johnson - assassination of John Kennedy
* Gerald Ford - resignation of Richard Nixon
Now, if you do the maths, of the 42 presidents (no, not 43) you've ever had, 9 have been promoted from the office of Veep. That's a 27% chance Palin will be president of the US on past form, not even taking McCain's health into account. Over one-in-four chance she will be president if McCain wins the election.
Once? Maybe? Are you kidding?