Is that a rule or a norm? Norms don't exist anymore.
Constitutionally the electors from a State can't vote for a President and a VP both from their State.
Thus, unless Harris could re-register elsewhere they'd give up California's EVs for the VP slot.
There are 538 EVs:
- 1 for each Congressional District
- 1 for each Senator
- 3 for DC
538/2=269.
In 2016 Biden/Harris got 306. California has 55 so if you take those away:
306-55=251, NOT a majority.
IIRC if there is no majority:
- HoR elects POTUS but the election is by State with each delegation getting one vote
- Senate elects VPOTUS
Here is where it gets REALLY screwy. I *THINK* the Senate that makes the decision would be the one elected this fall, not the current one, but I think that Harris, as current VP would get a vote.
The Senate is currently REALLY close at 52-49 Democratic including Harris (as VP).
I have no idea what happens if the Senate deadlocks and can't break the tie and this isn't completely implausible, consider:
- R's gain 1 seat net, that gets us to 51-50 D
- One Democratic Senator dies or is otherwise incapacitated.
- Alternatively Rs gain net two then one R dies or is incapacitated.