What Boris needs to do is cut a BINDING deal with Trump, and then he won’t have to worry about being screwed, should Harris/Hillary win.
As I understand it there would not be time to cut a deal and get it ratified before January even if it was agreed tommorow.
Trade deals take month’s to negotiate. For instance, right now the UK wants to protect its farmers from American agriculture, which has lower prices due to economies of scale. At the same time the USA farm lobby is having none of that. So the trade talks have stalled