Every poll (even by fox) have him trailing Biden by a significant margin. Trump, however, brings up imaginary polls in which he's winning and adds that he shouldn't accept any other outcome. I can provide links to both of these claims if you don't believe me, but I think you do. Unless I'm mistaken, you see these two facts as unrelated, and the latter as (perhaps badly communicated) optimism. Because after all, he's got to be optimistic about his chances to stay in the race for the next four years in office... Right?
... But then there's that third fact : his suggestion to delay the election. Can I take your "You've got to beat him first." as a sign that you disagree with this suggestion?
I don't see Trump behaving much differently than he did in 2016. By that I mean, exactly the type things you mention above, mainly that he dismissed the popular polls as unreliable. On the night before the election, the major news networks were all still talking about a 90%+ chance that Hillary Clinton was going to win. She didn't win. And I know her people just love to talk about how she won the popular vote, but the popular vote doesn't really count for anything. Well, unless a State passes a law that binds their electors to voting for the result of their States' popular vote tally. We do now at least have some clarification from SCOTUS on that, i.e. that electors can be required by their State legislatures to vote for the candidate who won in their state. But it is the electors that choose the next President.
So when I said, "You've got to beat him first," I only meant "don't count chickens before they hatch." Trump may be defeated in this election, but it hasn't happened yet.
As for Trump's mention of the date of the election, I think that was an intentional troll, something that twitter account is prone to. (I have my doubts that Trump himself is the author of those messages ... he has the best people working on it, fabulous people, classy people) He didn't actually propose that the date be changed, he "aired" the idea to get the left wigged out about it. He doesn't have the authority to change anything, which is why I'm sure of that. It is extremely, and I do mean
extremely, unlikely that the date of the election will be affected in any way. I only leave open the slight possibility because the reopening of schools nationwide in the next few weeks could lock us all down again, and then what? That would be a terrible mistake, but one thing I've learned in 2020 is that local State government leadership in the US is capable of even bigger mistakes than the Fed.
But if you want to get technical about it for the sake of argument, there is nothing in the Constitution that mandates when the election is held, it is a matter of State law. The real election that matters is the elector's in December, and even that doesn't have a set (by the Constitution) date. The only Constitutionally mandated date is the end/beginning of the next term, i.e. January 20. We have a lot of traditions and
local laws in the US that people are just very, very used to, but they're not actually 'set in stone' (or the Constitution).