Basically no other metric besides polling suggests any sort of Trump landslide.
It doesn't have to be a landslide even if Trump outperforms his polling. The polls just have to narrow between now and Election Day (or, more likely, flip to a Biden lead instead) in order for that to happen.
Demographics and demographic changes in key states.
I think if you look at the trends within each group individually, on the whole there are more promising signs for the GOP than the Democratic Party long-term.