The 20th Amendment allows leaders of the party of the popular-vote winner to select a new presidential candidate if the winner dies before the Electoral College meets. The college would then vote on that selection. If the popular-vote winner dies after the college meets but before the inauguration, the winning candidate for vice president becomes president. Neither of these provisions has ever been applied.
http://www2.worldbook.com/features/p...html/roads.htm
Not exactly what you asked, but it implies a special convention to me