Easy.
The 'Contingent Elector illegal scheme'.
The plan :
- have Pence defy the Constitution and not read the proper and legal name of State selected Electors on election day and instead to read the fake and illegal slate in to the record
- this causes a Connotational Crisis as State chosen electors which are supposed to be ceremonial read by VP are rejected by the President of the Senate for no reason
- The Constitutional remedy when the Senate cannot settle elector issues is to push it to an COntingent Election vote in the House to decide these matters
- The House, for a Contingent Election was controlled by Republicans, who if they all vote together would then put Trump back in power
- The Supreme Court (Judicial Branch) has NO role in such disputes via the Constitution, so even though Dems would surely sue, the Trump plan was to ignore any SC rulings as unconstitutional while citing the House (Legislative Branch) has solved this.