This may be the cynic in me but I think he’s just saying that as part of his efforts to invalidate an eventual loss. He’s doing this multiple ways
1. Using Covid as an excuse to propose a delayed election, knowing darn well it’s not something he can do, but now he’s planted the seed of “should this election happen” in some minds
2. His deliberate attacks on the USPS. This dates back some months, but the worse shape the USPS is in the more likely it is that not all mail in ballots will be counted.
3. When interviewed recently he was asked if he would accept the results of the election. He won’t answer with a straight answer. He’s said “we’ll see”. That’s insane on its own face value, but the message he’s communicating by answering that way is even scarier. He’s basically making it seem like accepting the results of the election is optional, if it comes out to his liking. This of course makes his base think the same way.
I’m sure there are other things I’m not thinking of but seeing a sitting president attack an election, and not just an opponent, really makes my stomach turn.