Honestly, unless the next scandal is incontrovertible proof that Trump set a child on fire at some point, I can't imagine it meaningfully harming him. Anybody still supporting him has justified the previous 50 scandals and it would be illogical for the fifty-first to matter
There were like 100 scandals before pussygate too and that one still hit him pretty badly. The biggest danger for Rubio is too many Republicans staying home because of a scandal breaking a few days before election day, and it's a very real danger. I am not confident about this race at all.