Indeed. IA and NH are probably the single biggest reason early national primary polls are wrong so often.I don't think it should be underestimated how much the early press influences how voters vote in later contests
Ie I don't think Trump would have won had he not won NH. The "loser" narrative would have started after losing both the first to states.
If Biden wins IA, NH, and SC the race is over regardless how many voters or what percentage he wins them by
The good news is Biden slightly underperformed iowa in 2008 and appears to be doing the same in 2020 polling. I think he'd be pretty screwed if he lost Iowa, seeing how much of his pitch is electability and inevitably.