If a candidate dies after receiving their party's nomination...

[Gary J]

A practical difficulty might arise if a winning candidate was to die on the day the electors were due to cast the formal electoral votes. There would probably be no time for a new official nominee to be named.

Would Congress have to investigate if electoral votes for the deceased candidate had been cast before or after their death or before or after their death was known? Alternatively Congress could disregard the Greeley precedent and just count all votes for the deceased candidate (which might be the best solution, on the basis that someone who was alive at the start of the day of election should be regarded as available to receive votes all day precisely to avoid the confusion that might otherwise result).

If electoral votes for the deceased candidate were disregarded and this resulted in no candidate receiving a majority of electoral college votes, there would have to be a contingent election (election by House delegations amongst the top three candidates receiving valid electoral votes for President or election by Senators amongst the top two recipients of Vice Presidential electoral votes). That might lead to the party which "won" the Presidential election not having a candidate for the contingent election or having to elect someone who had only received one or two electoral votes from faithless electors (or the candidate who had been lucky enough to receive the highest number(s) of electoral votes if the majority party electors had heard of the original nominees death in time to splinter their votes between random prominent people).