Fun fact
If a candidate dies before the general election but after they've secured their party's nomination, it's a relatively simple fix: The deceased candidate's party picks a replacement and that replacement is on the ballot on Election Day.

If a candidate dies after the general election, it gets more complicated.
If a candidate dies between the popular vote and the meeting of the Electoral College the parties follow the same process to fill the vacancy on the ticket. If the candidate that dies is on the...

winning ticket, it's still the party's responsibility to provide a new candidate their electors could vote into office.
But here, the political implications are more serious because it takes some of the power away from the people; they don't get to vote again. ..

The replacement candidate's name goes on the Electoral College ballot only, and their political party expects its electors to vote the replacement candidate into office.
There's no federal law saying the electors have to vote for the new candidate....

Theoretically, if the candidate to whom they pledged their votes dies and their party doesn't name a preferred successor, electors could vote for the party's VP candidate, a third-party candidate or a leading contender within their own party. But state laws vary on the matter...

But what if the president-elect dies — meaning the winning presidential candidate dies after the election but before the inauguration on Jan. 20?

The 20th Amendment of the U.S. Constitution provides that if the president-elect dies, the rules of succession apply, and the...

vice-president-elect becomes the president-elect. Unfortunately, it's not clear when in the process a winning candidate becomes president-elect.

The winning candidate definitely assumes the title president-elect after Jan. 6, when Congress officially counts the Electoral...

College votes and declares a winner. But a winning presidential candidate has never died before being inaugurated, so Congress has never had to define president-elect....

If the winning presidential candidate dies between Dec. 15 but before Jan. 6, Congress would have to decide whether to count the votes cast for them. If Congress chooses to validate the votes, the laws of presidential succession are carried out, and the winning candidate's...

vice president becomes president-elect. If Congress chooses not to validate the votes, however, the question will be whether the living candidate has a majority of the overall electoral votes. If they don't, then the 12th Amendment says the House of Representatives must...

elect the president from among the three candidates with the most votes.
In a two-person race, then, the breathing candidate wins.
In 2020, the people vote on Tuesday, Nov. 3; the Electoral College votes on Dec. 14, 2020; and Congress counts the electoral votes on Jan. 6, 2021.