Assuming that any of the Hunter Biden rumors are remotely true, there are two things to remember:
1. Hunter Biden is not on the ticket and voters realize this. This is like Trump voters abandoning him en masse because it came out that Eric or Don Jr. cheated on his taxes or his wife. Nope, that wouldn't sway them.
2. Trump ushered in a new era of "No Shame" politics in 2016. Think about it, despite all of the evidence of infidelity, payoffs, tax issues, charity fraud, possible rapes and sexual assaults, friendship with Jeffery Epstein, etc., he still got elected.
So, if a candidate had an affair, a porn addiction, sold weed in college, did some blow off a stripper's belly in 2010, has three failed marriages, attended a furry convention, or anything like that, it pales in comparison to anything that Trump has done. Voters go, "Meh. I still like his policies and at least he admits it without trying to cover it up." and treat it like an offsetting penalty in football. Trump has opened the door for imperfect people that would have been shut out in years past.