The confidence I've been seeing from Trump supporters is astounding given how far behind he is and has been since March. Counting on massive polling errors, both nationally and in state polls across multiple states, seems like a poor reason to believe Trump is favored. If TX was Trump+16 and AZ was Trump+6 I don't think pundits would be saying the race is a pure tossup.
Trump supporters have make it clear that they do not believe the polls, and that the polls are being "rigged" to disadvantage Trump. Many of them have also said that the polls are underestimating the true extent of Trump's support. And in addition to all of this, they have bought into the conspiracy theories which say that voter fraud will work to the advantage of Biden and Democrats this year, as it supposedly did for the Democrats in 2018 and for Clinton in 2016.
