What happens if a presidential nominee dies during the campaign?

John McCain, for example, is already in his 70's. If the nominee dies, how does the party pick another candidate?





(*I don't care about predictions on how healthy McCain is. I am asking about government procedure.)What happens if a presidential nominee dies during the campaign?
They throw the person in the ground or an incinerator and move on.What happens if a presidential nominee dies during the campaign?
William Henry Harrison - April 4, 1841, died of pneumonia after giving a long inaugural address in the cold and rain.


It wasn't his campaign but he never got to really do anything after being elected president and when he died his vice president naturally took the presidency.





I would assume that if McCain died now, the rep. party would probably just go down the list ex. Mitt Romney or if McCain has an unofficial or official vice president (unknown to the public that is) then the Vice would take his place on the ballot.
The party picks a new model and crosses their fingers.
The party will have to reconvene and select a new candidate