Depending on how the event is spun (story-wise), an attempt like this could make the other candidate’s party seem unhinged enough that one of their members would do (and apparently fail badly at) this. This, making the target, and their party by association, seem more noble than thay may be.
To a lot of people, whether the shooting is or isn’t affiliated doesn’t really get questioned no matter what they hear, as what party would hurt itself? They’ll immediately think there is some conspiracy (the human psychology loves these rabbit holes) to make it seem like any favoring affiliation to the target’s political side is staged by the other.