[null and void]

I think this is the summary.

Before election:

•DNC decides, method not specified
•RNC fills vacancy, reconvene convention or RNC state representitves vote, simple majority wins

Just before the election:

•Congress may pass special legislation to move back election day to give more time for the party to select a new candidate and regroup

11/4 Election

After election, but before Electoral College

•No federal law. Electors open to vote for VP, third party, or convention runner up. State laws may affect elector's abilities to select.

12/15 Electoral College

After Electoral College, before Congress counts the votes

•Congress counts Electoral College votes and declares winner. Winner's VP gets it

-or- •Congress throws out votes. If a surviving candidate can be said to have a majority of votes, they get it. -or- •Congress throws out votes. Per 12th Amendment, House of represetitives selects from top three candidates with the most votes. (surviving Democrat or Republican and two third party candidates?) -or- •Per 20th Amendment, VP gets it, but only applies after candidate becomes 'President-Elect". That could be after Electoral College.

1/6 Congressional Vote Count

After Congressional count but before inauguration;
•Per 20th Amendment, VP gets it, but only applies after candidate becomes 'President-Elect" That is certainly after Congressional count.

1/20 Inauguration
•VP gets it