Let’s start with Arizona. Biden had a 6 point advantage in a New York Times/Siena College poll put out on Sunday. CNN/SSRS had Biden at 50% and Trump at 46% on Saturday. The average poll overall has Biden up by 4 points. So Trump needs a larger than average polling error in a state where there hasn’t been a tradition of polling errors favoring Republicans.
If Trump is able to overcome that, he’ll still need to go into Pennsylvania and win there. (There’s a reason Trump has been barnstorming the state.)
Three polls out this weekend show similar results in the Keystone State. Biden was up 5 points in a Muhlenberg College poll (well within the poll’s 5.5 point margin of error), 6 points in a New York Times/Siena College poll and 7 points in an ABC News/Washington Post poll.
Overcoming an average 6 point polling deficit is possible. It’s quite hard though. It’s basically a little less than the chance of flipping a coin in the air three times and having it land on heads all three times.