Charlie’s right.
Something very extreme and very unlikely would have to happen–like multiple assault allegations against Biden or a complete economic recovery–for Trump to recover in the polls and win the election.
The public is simply sick of Trump’s antics and his poor COVID governance, and I don’t think there’s any way to change that enough to ensure victory.
However, if Trump resigned, and Pence chose a good VP, he would have a better chance. Pence is a refreshingly “normal” politician who is a good speaker and a solid conservative and avoids saying anything extreme or offensive. He’s the kind of person most Republican voters would have preferred as president anyway (Remember, Trump won a plurality, not a majority, of votes in the primaries.)