Not sure how that's true. Biden's never faced a tough national race before, he failed so quickly in his previous two presidential campaigns that the opposition research didn't even come out. You know they're actively chasing more Hunter Biden revelations right now? You know that one of the first words Independents think of when asked to describe Biden is "corrupt"? Representing Deleware and all, you don't think that Biden has even more corporate connections, even more examples of setting up his family in lucrative positions (Hunter isn't the only one), even more times when he "compromised" on bad positions? You don't think the Republicans are going to target Black and Latino folk on Facebook with constant Crime Bill messaging, Biden's fight to stop busing, Biden bragging about being able to work across the aisle with White Supremacists, Biden blaming Black parents and Black kids for poor school performances, etc.?
Not to mention that Biden's own gaffes are going to just get worse the more he declines and the more national coverage he gets. You really think this on a daily basis is a good look?
Trump is going to be all "corrupt Biden", "sleepy Biden", "creepy Biden", "senile Biden." Meanwhile for Bernie, Trump's going to say "he's a socialist!" which everyone already knows and which Republicans say every year about every Democrat anyway. Besides that?