Article II, Clause 4. The Congress may determine the Time of chusing the Electors, and the Day on which they shall give their Votes; which Day shall be the same throughout the United States.
By constitutional authority, congress has set the day by statute:
3 U.S. Code § 7.Meeting and vote of electors:
The electors of President and Vice President of each State shall meet and give their votes on the first Monday after the second Wednesday in December next following their appointment at such place in each State as the legislature of such State shall direct.
So ultimately, yeah, there is a constitutional basis for teh Electoral College to decide things tomorrow.
The date chosen is statutory, not constitutional.
The Court may disregard the statutory date set for tomorrow and proceed with this emergency.
The Electoral College is now on notice that whatever business they conduct between now and January 20, 2021 can be set aside.
Whether the Court acts on this or not, the events of December 18, 2020 will start.
You’re living down to your screen name.
“...following their appointment at such place in each State as the legislature of such State shall direct.”
Some states are still unresolved.