I'm sorry, but I don't think a poll where Biden has 49% and Trump has 46% is "good news for Democrats"
Especially when a significant portion of those who supported Biden in such a poll aren't thrilled about it.
Further likely fewer than 60% of eligible voters will even vote. There are a lot of people alienated from and apathetic towards the political landscape despite many dramatic events and high-stakes issues.
It's a difficult topic because it can't be reduced to a single reason.