Donald lost the popular vote the time he got elected and he wasn't near the polarizing figure he was in 2020. Yes, he gained voters. I don't deny that, but numbers indicate that he also alienated huge swaths of the electorate too. Those people didn't need to turnout to support Biden because Trump energized them to turnout against him. I actually give Trump a shit ton of credit for being amazingly influential. It was just a lot more negatively so than positively and that drove voter participation to levels not seen in a century. All Biden had to do was a) be opposite Trump and b) not be as "guess she is the lesser evil" as Hillary in 2016. That's it. That's the big fucking secret to his success.
