Anytime there are such large numbers of "undecideds" it's likely they are low-information, and an opportunity for Trump (or any unscrupulous politician, but really, Trump) to lie to them and turn them to whatever side they wish.
The amount of propaganda on TT is rather huge, though I won't say any different than US media, just more of it these days oriented to how 'good' China is.
If tomorrow China becomes a global beacon of high-quality and affordable healthcare, maybe US will actually feel some pressure to fix its issues.
Vote for your congress members.