Now; definitely Biden (25th Amd US Con)
From the time the electors met in DC until Jan 20; probably Biden.
Pre-election; probably up to DNC, emergency meeting ,etc.
From Election to time Electors met in DC until Jan 20; a legal sh*tstorm that would make Bush-Gore look like Small Claims Court.
(PS, this guy I called in LA is good. I always cribbed off his Con Law notes, he from my Advocacy papers!)