What happens if presidential candidate dies?

[Darren_Garrison]

Earlier thread:

All Presidential candidates are dead--Constitutional question.

Thinking about how both Trump and Biden/Sanders are old enough to be in the higher risk category for the coronavirus, it made me wonder: the Presidential candidates for both main parties are locked in in the primaries. But before the election, for whatever reason, both of them die. What happens? Is the election postponed? Do the “runners-up” get their places? Are there provisions in place for this hypothetical?