The fact that even all this pro-R "unskewing" where we lazily assume that the same polling error occurs again AND to the same extent (which wasn’t the case in 2018) only yields a map where Biden is already at 278 EV is pretty devastating for Trump.
I don't think so. I think we might be at a crossroads for polling. In the same way the "New York Times" and major newspapers or late night TV like "The Tonight Show" are now essentially arms of the left, we may see polling join that group, especially if polls overestimate Biden like they did many Democrats since 2014.
I’m not saying that the race couldn’t tighten a little or that there aren’t polls which are understating R strength, but the big picture has been clear, unambiguous, and consistent since 2017. Biden's lead in national polls has been larger and more stable than Clinton's ever was (in case we forget, national polling wasn’t dramatically off in 2016), and he’s polling far better than her in several swing/R must-win states (especially MI, TX, GA, AZ; and in those last three states polling has not exactly underestimated R strength in recent elections).
It’s more than polling, though. From an electoral standpoint, his entire presidency has been a disaster for the GOP, and I’m not just talking about low-turnout special elections here. There’s no denying on my part that midterm elections have tended to result in some serious losses for the incumbent's party in recent history, but when you consider how much Republicans had going for them in 2018 (galvanized base and high turnout, booming economy, Kavanaugh aftermath, most lopsided/pro-R Senate map since 1938, no major war like in 2006, etc.), it’s astonishing how devastating the defeat was for the party. That election should have never been another 2006 or worse.
COVID-19 and the protests have made things worse for Trump, but it was obvious even before those developments that this election was going to be an uphill battle for him without a historically unpopular opponent to run against and his inability to broaden his base (all the while losing ground in vast parts of the country that were key to his victory in 2016, especially in suburban areas/among female voters/"lesser-of-two-evil" voters/etc.). Trump has always been an unusually weak position for an incumbent (it’s been this way since January 2017, honestly), but much of it makes sense if you interpret 2016 not as an embrace of Trump but as a rejection of Hillary Clinton. He’s as close to DOA as you possibly get under current conditions.
E: There’s nothing wrong with being cautious and refusing to blindly trust polling, but I’d definitely advise against trusting your "gut feeling" too much lest you set yourself up for disappointment. I know the feeling because my "gut" told me that 2014 and 2016 would be much better elections for the GOP than predicted by most election observers, but my "gut" has disappointed me just as often if not more during Trump's presidency.
