It is unlikely that Trump is going to pull this one out despite what the Republicans who think that there is a large undercurrent of "silent Republicans" out there who will bring it home for him.
In 2016 you had the two most unpopular candidates in the history of Presidential elections (at least in the 100 or so years when they started keeping such statistics). The two candidates had the largest negative approval ratings in recorded history. Biden is nowhere near as unpopular as Clinton won (his negative rating is double digits lower than either Clinton or Trump ratings from 2016 or Trumps rating in 2020).
Second, Trump has lost about 2% of his supporters over the last 4 years. That may not seem like much, but you have to remember that Clinton won the popular vote and Trump only won the electoral college by about 80K voters in WI, MI and PA. With nearly 63M voters who voted for Trump, the loss of 2% of his support is the loss of about 1.2-1.3M voters. And quite a lot of those losses are in swing states.
Conversely Biden has lost virtually none of Clinton's supporters and he has actually gained some. Some of the Sanders supporters who boycotted the election when Sanders lost the controversial DNC candidacy will be voting this year. Additionally, roughly 6% of voters voted for 3rd party candidates and the number of voters supporting third-party candidates have plummeted and Biden is getting about 2/3 of those voters to Trump getting 1/3 of those voters.
There are very few gains for Trump compared to 2016. So, basically, his only desperate ploy is to try and decrease attendance at the polls and prevent Biden voters from actually voting. This is why he is opposing mail-in voting, why he has had Louis DeJoy sabotaging mail delivery and why he is trying to get election officials to restrict the number of polling stations. The states hardest hit by the elimination of mailboxes and mail sorting machines are all swing states and the USPS under DeJoy has targetted Democratic neighborhoods and polling districts in an explicit ploy to prevent Democratic voters from voting. If you look at states that have restricted polling stations for the November elections, there is a high concentration of polling stations in heavily Democratic areas especially ones with low income or senior voters, two demographics which are leaning heavily left this election.
So, the Democrats need to counter the voter suppression going on. If they can keep the voting representation high, Trump will not win. If Trump gets away with suppressing the vote, he stands a chance.
https://www.npr.org/2020/08/08/900338253/why-the-2020-presidential-election-is-not-2016
https://www.newsweek.com/decommissioned-mail-sorting-machines-swing-states-could-define-election-1526866